Topic: change list of topics
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	How to calculate percentage change		2007-08-03
		From Galland: I am working on graphs and I need to find the percentage of increase from one figure to another. How do I do that? For instance staff hours for 2006 were 28011 and for 2007 were 31230. How do I find the percentage of increase? Answered by Stephen La Rocque.
	Sipping juice from a Tetra Pak		2020-02-11
		From Anjhelic: Karen is sipping juice from a 1 in. by 3 in. by 6 in tetra pack at the rate of 0.5in³/sec. How fast is the height of juice in the pack decreasing? Answered by Harley Weston.
	Percentage change in refractive error		2019-04-04
		From Ammara: Hi, I'm trying to figure out how a paper I'm looking at has found a percentage from the numbers below. its a paper comparing two lenses. it says that the new lenses 'slowed the progression of refractive error by approximately 50%'. the refractive error with the old lenses was -2.26 after two years it was -3.28 the refractive error with the new lenses was -2.24 after two years the refractive error is - 2.75 Thank you so much for your help it is most appreciated! Answered by Penny Nom.
	Related rates		2018-02-11
		From angelo: hi admin please help me answer this question. thank you! At a certain instant of time, the angle A of a triangle ABC is 60 degrees and increasing at the rate of 5degrees per second, the side AB is 10cm and increasing at the rate of 1cm per second, and side AC is 16cm and decreasing at the rate of 1/2 cm per second. Find the rate of change of side AB? Answered by Penny Nom.
	Heat equation		2017-11-23
		From Max: What does du\dt=a(triangle)^2u mean. Can it be solved for t. Answered by Penny Nom.
	How many miles did he drive in one hour?		2017-11-21
		From Ava: Graham drove 42 1/3 Miles in 1 1/3 hours. How many miles did he drive in one hour? Answered by Penny Nom.
	The distance between the origin and a moving point on a graph		2017-10-16
		From Paulina: Find the rate of change of the distance between the origin and a moving point on the graph of y=x^2 +1 if dx/dt=2 centimeters per second Answered by Penny Nom.
	Percentage change in productivity		2017-03-15
		From Sunni: I'm working on a graph and I need to find the percentage of increase from one figure to another. How do I do that? For instance our department started with a workload of 1773 in Jan and ended with 341 in Dec. In addition to that we received 2088 new items from Jan - Dec with an average of 5 workers. How do I find the percentage of increased productivity if any? Answered by Penny Nom.
	The average rate of change of cot(t)		2017-01-18
		From Brianna: Hello! It's been a while since I've taken a math course, and I'm stuck on a problem in my calculus course. The question is this: Find the average rate of change of the function over the given interval. h(t)=cot(t) a) [5pi/4, 7pi/4] Answered by Penny Nom.
	Water leaking from a trough		2016-12-28
		From Kathryn: A trough is 6 m long, and has uniform cross-section of an equilateral triangle with sides 1 m. Water leaks from the bottom of the trough, at a constant rate of 0.1 m3/min. Find the rate at which the water level is falling when the water is 0.2m deep. Answered by Penny Nom.
	Percentage change		2015-01-14
		From Jim: When using a scale e.g. 0-10, what is the formula for calculating percentage change. For example when someone answers a questionnaire where a question has a 0-10 scale, and they score a 4 first time, and then they answer the same questionnaire a different day, and they score an 8, how do I calculate the percentage change. Answered by Penny Nom.
	Percentage change		2014-05-09
		From hi: the hw club had 46 members in sept. in april, the club had 24 members. what was the percent of change in the hw club's membership from sept. to apan increase or decrease in membership? ril? what is Answered by Penny Nom.
	$9.50 in coins		2014-01-15
		From dana: you have $9.50 in coins. it has twice as many nickels as quarters and three times as many dimes as nickels. how many of each coin do you have? Answered by Penny Nom.
	When would one flip the inequality sign?		2014-01-09
		From Natasha: Would one flip the inequality symbol in this equation: (explain why) (-9a)/(-9) > 81 And please explain in what circumstances one would flip the inequality sign THANKS! Answered by Penny Nom.
	Percent change in sales		2013-06-04
		From Sui: Hi, I would like to ask your favor for reviewing the following percent change in sales calculation, did I do it right? I am surprise/wondering with the big amount of the percentage result. Your assistance and guidance would be highly appreciate. Sales for month of August 2000: 5,198,750 IDR Sales for month of October 2000: 62,291,700 IDR Difference = 62,291,700 IDR - 5,198,750 IDR = 57,092,950 IDR Percentage change = 57,092,950 IDR : 5,198,750 IDR = 10.98 X 100 = 1,098% Sales for month of February 2008: 1,664,800 IDR Sales for month of August 2008: 161,715,307 IDR Difference = 161,715,307 IDR - 1,664,800 IDR = 160,050,507 IDR Percentage change = 160,050,507 : 1,664,800 = 96.14 X 100 = 9,614% Thanking you, Sui Answered by Penny Nom.
	Inverting fractions and percentage		2013-05-18
		From Carlos: If I calculate the percentage change between two fractions, say, 1/100 and 2/100, I get 100% change. Now, if I flip denominator and numerator, 100/1 and 100/2, and repeat the calculation, I get a 50% change. Why are the percentages different? Thank you very much Answered by Penny Nom.
	Increasing and decreasing sales		2013-03-06
		From Meghan: Pace Design's sales increased by 30% in the first year, increased by 60% in the second year, decreased by 60% in the third year and increased by 90% in the fourth year. What was the cumulative change in sales over the 4 years? Answered by Penny Nom.
	Related rates		2013-02-17
		From Ishaak: A hemispherical bowl is filled with water at a uniform rate. When the height of water is h cm the volume is π(rh^2-1/3 h^3 )cm^3, where r s the radius. Find the rate at which the water level is rising when it is half way to the top, given that r = 6 and the bowl fills in 1 minute. Answered by Penny Nom.
	How fast is the distance between the aircraft and the car increasing?		2012-10-24
		From Steven: At a certain instant an aircraft flying due east at 240 miles per hour passes directly over a car traveling due southeast at 60 miles per hour on a straight, level road. If the aircraft is flying at an altitude of .5mile, how fast is the distance between the aircraft and the car increasing 36 seconds after the aircraft passes directly over the car? Answered by Penny Nom.
	Percentage change		2012-04-19
		From Christine: For my intermediate macroeconomics class, there is a question about percent change. The numbers are: Quantities of oranges in 2010: 104 Quantities of oranges in 2009: 100 How would I calculate to find the percentage change in quantities? Answered by Penny Nom.
	The spread of a rumor		2012-04-09
		From Roohi: The function f(t) = a/(1+3e^(-bt)) has also been used to model the spread of a rumor. Suppose that a= 70 and b=3 0.2. Compute f(2), the percentage of the population that has heard the rumor after 2 hours. Compute f'(2) and describe what it represents. Compute lim t approaches infinity and describe what it represents. Answered by Penny Nom.
	The period T of a pendulum		2012-03-27
		From Ashley: The period T of a pendulum is given in terms of its length, l, by T=2pi sqrt(l/g) where g is the acceleration due to gravity(a constant) a. find dT/dl b. what is the sign of dT/dl c. what does the sign of dT/dl tell you about the period of the pendulums? Answered by Penny Nom.
	Water is flowing into a cup		2011-12-19
		From Tim: A cup has a radius of 2" at the bottom and 6" on the top. It is 10" high. 4 Minutes ago, water started pouring at 10 cubic " per minute. How fast was the water level rising 4 minutes ago? How fast is the water level rising now? What will the rate be when the glass is full? Answered by Penny Nom.
	A cube of ice is melting		2011-12-05
		From Emily: a cube of ice (i.e.) each side is of the same length) is melting at a rate such that the length of each side is decreasing at a rate of 5cm per hour. how fast is the volume of the cube decreasing (in cubic cm per hour) at the instant the length of each side is 25cm? Answered by Penny Nom.
	Water pouring into a conical tank		2011-11-21
		From Patience: Hi my name is patience and I'm having a problem with this question. Water pours into a conical tank of semi vertical angle 30 degrees at the rate of 4 cm^3/s, where h is the depth of the water at time t. At what rate is the water rising in the tank when h = 10 cm? Thank you Answered by Penny Nom.
	A reservoir has the shape of an inverted cone		2011-10-03
		From Roger: a reservoir has the shape of an inverted cone whose cross section is an equilateral triangle. if water is being pumped out of the reservoir at a rate of 2m^3/sec, at what rate is the depth of the water changing when the depth is 40 meters? Answered by Penny Nom.
	A hemispherical bowl with a lead ball inside		2011-09-27
		From Jean: "(a) Water is being poured into a hemispherical bowl of radius 3 inch at the rate of 1 inch^3/s. How fast is the water level rising when the water is 1 inch deep ? (b) In (a), suppose that the bowl contains a lead ball 2 inch in diameter, and find how fast the water level is rising when the ball is half submerged." Answered by Penny Nom.
	The height of a fluid in a horizontal tank		2011-07-24
		From jason: Same set up as many others, cylindrical tank on its side, but I am interested in defining the change in volume and/or fluid level as a function of time at a constant volumetric outflow. I plan on hooking a pump to the tank so "gpms' will be constant. I have a couple different sized tanks and pumps so I want a general equation. Thanks for your help. Answered by Harley Weston.
	A conical container and a spherical balloon		2011-04-06
		From Steven: Water is running out of a conical container 12 feet in diameter and 8 feet deep (vertex down) and filling a spherical balloon. At the instant the depth of the water in the cone is 4 feet, the radius of the sphere is approximately 4 feet. The rate of change of the depth of the water in the cone at the instant is approximately ______________ times the rate of change of the radius of the balloon. Answered by Penny Nom.
	Two ships		2011-04-05
		From Gevork: Ship A is sailing due south at 16 mph. At the same time, a second ship B, 32 miles south of A, is sailing due east at 12 mph. (a) at what rate are they approaching or separating at the end of one hour? (b) At what rate are they approaching or separating at the end of two hours? (c) When do they cease to approach each other and how far apart are they at that instant. Answered by Penny Nom.
	The rate of change of the area of a parallelogram		2011-04-05
		From Gevork: Let a parallelogram have sides of 8 and 12 and let vertex angle A be decreasing at a rate of 2degrees per minute. Find the rate of change of the area of the parallelogram when angle A equals 30 degrees. Answered by Penny Nom.
	The rate of change of (8e^3x)+(27 e^-3x)		2010-11-23
		From Aleo: I am unable to solve this problem: Find the rate of change of (8e^3x)+(27 e^-3x), with respect to x when x= 0.5 Answered by Penny Nom.
	The distance between the origin and a moving point		2010-09-24
		From Norma: I am having problems with this question find the rate of change of the distance between the origin and a moving point on the graph of the function below if dx/dt=5 cm/sec y=x^2+2 Answered by Penny Nom.
	A comparative report		2010-05-27
		From jo: Question from jo: I have a comparative report and I was confused about how to get the percentage of the current 1st quarter vs. last year 1st quarter, vs. last year of the same month. I hope you could help me, thank you. Example: Food sales: 3Day Sale Event TY: 1,352,293.58 May (Back to School) LY: 1,205,614.31 April (Summer Sale) LY: 1,065,693.40 May 2009 Answered by Penny Nom.
	The rate of change of y with respect to x		2010-04-29
		From Tom: I just had a quick calc question about wording that wasn't ever addressed in class. When the book says "the rate of change of y with respect to x", should it be considered how fast y is changing in comparison to x? I ask because the textbook says that "y is changing 3 times faster than x, so the rate of change of y with respect to x is 3." I'm use to rate being like velocity, as in units of distance per units of time. All we're told in class is that it's the slope of the tangent line, I was hoping you could clarify for me what exactly is meant by the wording of a "rate of change of something with respect to something else". More specifically, what "rate" and "with respect to" mean within this context? Thanks for your time Answered by Harley Weston.
	Cooling		2010-03-07
		From Lori: If a house is always at 20 degrees celsius. Water (tea) boils at 100 degrees celsius. 5 minutes later the tea was 70 degrees celsius. Use an equation to predict the temperature after 20 minutes. Answered by Tyler Wood.
	At what rate are the people moving apart?		2009-11-01
		From saira: A man starts walking north at 4 ft/s from a point P. 5 minutes later a woman starts walking south at 5 ft/s from a point 500 ft due east of P. At what rate are the people moving apart 15 minute after the woman starts walking ? Answered by Harley Weston.
	Pennies, nickels and dimes		2009-09-22
		From Kiadadh: Show 12 ways to come up with 28 cents using only pennies, nickles and dimes Answered by Robert Dawson.
	Percentage price change		2009-08-27
		From alicia: what is the percentage price change between R66-R10 if the answer between the two is R56 Answered by Penny Nom.
	Percentage decrease		2009-08-04
		From Bill: How to calculate the Percentage Increase or Decrease of a $ value. Example - Site Spend for 01-01-2008 thru 07-31-08 was $ 3,465,660 Site Spend, 2009 YTD as of 07-31-09, was $ 1,673,405 Site Spend down what % between these two amounts ? Answered by Penny Nom.
	Change 5/6 into a percent		2009-04-15
		From Shelly: My question is when it says change 5/6 into a percent Answered by Penny Nom.
	The rate of change of the volume of a sphere		2009-03-25
		From Kaylin: why the rate of change of volume of a sphere is not constant even though dr/dt is constant? Answered by Walter Whiteley.
	Related rates		2009-03-14
		From Jeevitha: The side of an equilateral triangle decreases at the rate of 2 cm/s. At what rate is the area decreasing when the area is 100cm^2? Answered by Stephen La Rocque.
	How fast is the visible surface of the earth decreasing?		2009-01-24
		From Ray: A dive bomber loss altitude at a rate of 400 mph. How fast is the visible surface of the earth decreasing when the bomber is one mile high? Answered by Harley Weston.
	In the shadow of a flagpole		2009-01-22
		From La: How fast is the length of the shadow of an 18 foot flagpole growing when the angle of elevation of the sun is 45 degrees and is decreasing at a rate of 10 degrees per hour? Answered by Harley Weston.
	Negative rate of change		2009-01-12
		From hemanshu: when i have to find rate of change of decrease in any value my ans comes in negative why?????????? Answered by Penny Nom.
	Related rates		2008-11-26
		From Lyudmyla: How fast is the volume of a cone increasing when the radius of its base is 2 cm and growing at a rate of 0.4 cm/s, and its height is 5 cm and growing at a rate of 0.1 cm/s? Answered by Harley Weston.
	How fast is the distance between the airplanes decreasing?		2008-11-10
		From Crystal: At a certain instant, airplane A is flying a level course at 500 mph. At the same time, airplane B is straight above airplane A and flying at the rate of 700 mph. On a course that intercepts A's course at a point C that is 4 miles from B and 2 miles from A. At the instant in question, how fast is the distance between the airplanes decreasing? Answered by Harley Weston.
	Melting ice on a hemisphere		2008-10-20
		From heather: The top of a silo is the shape of a hemishere of diameter 20 ft. if it is coated uniformly with a layer of ice, and if the thickness is decreasing at a rate of 1/4 in/hr, how fast is the volume of ice changing when the ice is 2 inches thick? Answered by Penny Nom.
	Related rates		2008-10-16
		From Gisela: As sand leaks out of a hole in a container, it forms a conical pile whose altitude is always the same as its radius. If the height of the pile is increasing at a rate of 6 in/min, find the rate at which the sand is leaking out when the altitude is 10in. Answered by Penny Nom.
	The rate of change of the volume of a cone		2008-10-15
		From Barbara: Suppose that both the radius r and height h of a circular cone change at a rate of 2 cm/s. How fast is the volume of the cone increasing when r = 10 and h = 20? Answered by Harley Weston.
	Bags of pennies		2008-10-11
		From paul: jenny divided 15 pennies among 4 money bags.she could then pay any amount from 1p to 15p just by giving bags.how many pennies did jenny put in each bag? Answered by Penny Nom and Victoria West.
	The average rate of change of gasoline used		2008-10-06
		From JHulie: What is the average rate of change of gasoline used, measured in miles per gallons if you travel 212 miles, then you fill your gas tank up again and it takes 10.8 gallons. If you designate your change in distance as 212 miles and your change in gallons as 10.8? Answered by Penny Nom.
	Vectors and an orientation change in the axes		2008-08-30
		From moumita: what differences take place to a vector because of choice of orientation of the coordinate axes and why?? Answered by Harley Weston.
	Trough Filling with Water		2008-08-21
		From lanny: a triangular trough is 10 feet long, 6 feet across the top, and 3 feet deep. if water flows at the rate of 12 cubic inches per minute, find how fast the surface is rising when the water is 6 inches deep. Answered by Janice Cotcher.
	Slope and rate of change		2008-06-23
		From Lee: What is the difference between a slope and a rate of change? Answered by Stephen La Rocque.
	Percent improvement		2008-06-12
		From JOHN: IF YOU HAD A RATE OF 678/HOUR AND YOUR NEW RATE/HOUR IS NOW 1961 WHAT IS PERCENT OF IMPROVEMENT Answered by Penny Nom.
	The rate of change in the depth of the water		2008-06-12
		From Liz: A rectangular pool 50ft long and 30ft. wide has a depth of 8 ft. for the first 20 ft. for its length and a depth of 3 ft. on the last 20ft. of its length and tapers linearly for the 10 ft in the middle of its length. the pool is being filled with water at the rate of 3ftcubed/ min at what rate is the depth of the water in the pool increasing after 15 hours? Answered by Harley Weston.
	The average rate of change		2008-03-29
		From Tom: For the function x/3x-1 find the average rate of change between the interval x=1 and x=5? Answered by Harley Weston.
	Percentage savings		2008-02-01
		From Donna: What is the percentage of savings if I bought an item for $98.60 that was $152.23 and something for $96.48 that was $136.65? Answered by Penny Nom.
	Percentage change		2007-12-19
		From Aaron: I understand how figure percent of change and I can figure it on a calculator but if I have to do it without I'm not sure how to divide when the original amount is larger than the amount of change. For example, the decreased amount is 5.00 on 29.99, what would the percent be. Like I said I can do it on a calculator but need to know how to figure it without one. Answered by Penny Nom.
	Percent change between two value ranges		2007-11-28
		From Joe: How do you calculate a percent change between tow value ranges - for instance if I project a range for 2007 to be between 100 and 120 and a range for 2008 to be between 120 and 140, how do I calculate the estimated increase between the range? Is it 0% to 40% (taking the two inside values rto calculate the minimum and the two outside values rto calculate the maximum?) Answered by Harley Weston.
	The rate of change of the concentration of a solution		2007-10-30
		From Nicholas: A barrel initially has two kg of salt dissolved in twenty liters of water. If water flows in the rate of 0.4 liters per minute and the well-mixed salt water solution flow out at the same rate, how much salt is present after 8 minutes? I tried working backwards given the answer but I can't seen to get their answer of ~1.7kg. Any help would be great! Thanks Answered by Harley Weston.
	The rate of change of the area of a triangle		2007-10-22
		From Ahlee: So my question is: The included angle of the two sides of a constant equal length s of an isosceles triangle is ϑ. (a) Show that the area of the triangle is given by A=1/2s^2 sinϑ (b) If ϑ is increasing at the rate of 1/2 radian per minute, find the rate of change of the area when ϑ=pi/6 and ϑ=pi/3. (c) Explain why the rate of change of the area of a triangle is not constant even though dϑ/dt is constant Answered by Penny Nom.
	The average rate of change of a function		2007-10-11
		From vern: Find the average rate of change of the function over the given interval. Compare this average rate of change with the instantaneous rates of change at the endpoints of the interval. f(X)=sinX for the inverval [0,pi/6]? Answered by Harley Weston.
	Percentage change		2007-08-21
		From Saleena: Hiya, my name is Saleena and I'm studying business at college. My question for you is what is the percentage change of turnover of the following supermarket. Turnover (Millions) - ASDA 2001 -10,732 2002 -12,188 2003 -13,326 2004 - 14,318 2005 -14,865 Answered by Penny Nom.
	The change in an average		2007-08-19
		From farah: the average height of a group of 25 students goes up by 2 cm when astudent of height 165 cm replaces a student from the group.what is the height of the boy who went out of the group? Answered by Stephen La Rocque.
	Percentage change		2007-08-19
		From nona: If inputs increase by 30% and outputs increase by 15%, what is the percentage change in productivity? Answered by Stephen La Rocque.
	Percentage change		2007-08-13
		From Karen: I need a formula for calculating percentages in Excel. For example, we = sold 4 units of an item one month, and 105 units the next. I need a = formula to calculate the percentage increase in sales units. Also, if = 5251 were sold one month and 651 the next, what is the formula for = calculating the percentage difference? Please help, thank you. Answered by Penny Nom.
	Buying and selling apples		2007-08-03
		From Priya: Gorang bought 60 Kg of apples at Rs 48 per Kg. He sold 70% of the apples at Rs 60 per Kg and the remaining apples at Rs 35 per Kg.Find Gorang's gain or loss percent on the whole transaction. Answered by Stephen La Rocque.
	Percent change over multiple periods of time		2007-06-07
		From Eric: I am trying to show the percent change over multiple periods of time. Is there a formula for the percent change over multiple periods or will I have to calculate the percent change for each previous period versus the year prior? Answered by Penny Nom.
	Rate of change of distance between the clock hands		2007-06-05
		From Jonathan: A certain Clock has a minute hand with a length of 4 inches long and an hour hand with a length of 3 inches long. How fast is the distance between tips of these hands changing at 9:00? Answered by Stephen La Rocque.
	Percent difference		2007-05-17
		From Carolyn: What is the % difference between these two numbers 211373 & 185420 Answered by Gabriel Potter, Penny Nom and Steve La Rocque.
	Percentage change		2007-05-01
		From katie: i no many people have asked about this but im still unsure what is percentage change i have my ks3 tomoro so please reply asap thankz Answered by Penny Nom.
	(a-b)/b = c		2007-04-27
		From Adam: What does (a-b)/b = c represent when c is a percentage? Answered by Penny Nom.
	At what rate is the area of the triangle changing?		2007-02-24
		From mac: two sticks 3.5 feet long are hinged together and are stood up to form an isosceles triangle with the floor. The sticks slide apart, and at the moment when the triangle is equilateral, the angle is increasing at the rate of 1/3 radian/sec. At what rate is the area of the triangle increasing or decreasing at that moment? Mac Answered by Penny Nom.
	A particle moving along a curve		2006-11-18
		From Rachel: a particle is moving along the curve whose equation is: (xy^3)/(1+y^2)=8/5 assume the x-coordinate is increasing at the rate of 6 units per second when the particle is at the point (1,2). a. at what rate is the y-coordinate of the point changing at that instant? b. is the particle rising or falling at that instant? Answered by Penny Nom.
	An aircraft and a missile		2006-11-18
		From Sarah: an aircraft is flying at a constant altitude with a constant speed of 600mph. an antiaircraft missile is fired on a straight line perpendicular to the flight path of the aircraft so that it will hit the aircraft at a point P. at that instant the aircraft is 2 miles from the impact point P the missile is 4 miles from P and flying at 1200 mph. at that instant, how rapidly is the distance between missile and aircraft decreasing? Answered by Stephen La Rocque.
	Wheat is poured on a conical pile		2006-11-17
		From Rachel: wheat is poured through a chute at the rate of 10 cubic feet per minute and falls in a conical pile whose bottom radius is always half the altitude. how fast will the circumference of the base be increasing when the pile is 8 feet high? Answered by Penny Nom.
	The rate of change of the perimeter of a square		2006-11-07
		From Karli: Find the rate of change of the perimeter of a square with respect to its area. Answered by Stephen La Rocque.
	A boat is being pulled towards a dock.		2006-11-06
		From Cassie: A boat is being pulled towards a dock. If the rope is being pulled in at 3 feet per second, how fast is the distance between the dock and the boat decreasing when it is 30 feet from the dock? Answered by Penny Nom.
	Percentage differences		2006-10-23
		From Michael: how do I calculate the percentage difference of a certain box size. for example. How much percent smaller is this box: 8.4mm x 6.3mm to this box: 9.35mm x 7mm Answered by Stephen La Rocque.
	How fast is the water level rising when the water is 1 meter deep?		2006-10-19
		From Don: The cross section of a 5-meter trough is an isosceles trapezoid with a 2-meter lower base, a 3-meter upper base and an altitude of 2 meters. Water is running into the trough at a rate of 1 cubic meter per minute. How fast is the water level rising when the water is 1 meter deep? Answered by Stephen La Rocque.
	Plotting percentage change		2006-10-11
		From Beckie: I have worked out a set of percentage differences which are all percentage decrease. Should i express them as a negative percentage as -20%? I also need to plot them on a graph and am not sure whether to just use the percentage difference as it is, in which case i get a positive gradient, or include a negative axis and plot them in this way, in which case i would get a negative gradient. I think the slope of the curve will be the same either way so it might not matter! Answered by Penny.
	The velocity of a pendulum, part II		2006-09-07
		From Erin: We saw the question in your database about the velocity of a pendulum swinging.....It is the same exact question....but there is another question......it says.... "estimate the instantaneous rate of change of d with respect to t when t = 1.5. At this time, is the pendulum moving toward or away from the wall? Explain." Answered by Harley Weston.
	Percentage weight change		2006-01-24
		From Abdul: what is the percent change if a person's weight changed over 3 years: year 1995 1997 1998 %change(1995-1998) weight 63kg 67kg 73kg ......... Answered by Penny Nom.
	Percentage change when you start from zero		2006-01-02
		From Joseph: I am not sure if my meaning for calculation for a percent change (C-P/P)x100) is correct. In this case, C=10, P=0, does this mean 100 percent increase from previous period? Answered by Harley Weston.
	Percent change		2005-12-17
		From Marie: What is the percentage change when 1500 becomes 2000? Answered by Penny Nom.
	Percentage increase		2005-09-19
		From Dory: Last year sales was 120,000 $ and this year sales is 280,000 $, there was an increase in sales. what I would like to know is the percentage increase between the years with the formula. Answered by Penny Nom.
	Is this percentage change or percentage increase?		2005-08-15
		From Betty: When calculating a percentage, if the formula is A(new) - B(old)/A(new) Is this percentage change or percentage increase? Answered by Penny Nom.
	Percent change		2005-07-01
		From Betty: Can you tell me the difference between Percentage Change, Percentage Increase, Percentage Difference and please give an example of each, I am very visual. Answered by Penny Nom.
	A rate of change problem		2004-10-15
		From Frank: Find the rate of change of the distance between the origin and a moving point on the graph of y = x(squared) + 1 if dx/dt = 2 centimeters per second. Answered by Penny Nom.
	Percentage change		2004-08-30
		From Lauren: if egg A weighed 55.4g and after 2 days it weighed 60.9g how could i calculate the percentage change in weight? Answered by Penny Nom.
	Rate of change problems		2004-08-01
		From Jim: I just want to check a couple average rate of change problems because i just guessed on how to do them. Can you tell me how to do them? the question says if f(x) = sqrt(x + 3), find f( x + rx). I got sqrt( x + rx + 3) the other two are : f(x)= 3x-1 (f(x) - f(1)) / (x-1) ... I GOT 3 & f(x)= x^3 - x (f(x) - f(1)) / (x-1) ... I GOT x^2 + x Answered by Penny Nom.
	x^2/3 - 7 x^1/3 + 12 = 0		2004-04-05
		From Jackie: I am having trouble solving this question for x: 1.) x^2/3 - 7 x^1/3 + 12 = 0 Answered by Penny Nom.
	x-6square root of x +8=0		2003-05-10
		From Elizabeth: x-6square root of x +8=0 Answered by Penny Nom.
	Percentage change in completion rate		2003-02-21
		From Remo: In the year 2000 300 out of a possible 600 completed a phone survey for a total of 50% completion rate. In the year 2001 20 out of 100 possible people completed the survey when it was re-done. This is a completion rate of 20% To figure out the percentage change between the years can just use the difference between the percentage figures I already have? Or can I calculate it the same as you would for non-percentage numbers. For example you gave an example here of a salary increase from $20 to $95 being an increase of 375%. Would I solve my problem the same way expect substituting my percentages (.5 and .2) in place of $20 and $95? Answered by Penny Nom.
	A penny, a nickel, a dime, a quarter, and a loonie		2003-01-21
		From Blaine: I have 5 coins: a penny, a nickel, a dime, a quarter, and a loonie. How many different amounts of money could I pay using any combination of these coins? Answered by Penny Nom.
	Averages of Averages		2002-12-21
		From Amy: If in the month of October the % of Payments Received was 80.74% and in November it decreased to 69.36%. Can you take the 80.74-69.36/69.36 to get the % of difference. In otherwords can you take the % of difference when the numbers you are comparing are %'s???? Can you also take an average of an average? For example, average number of payments received in October was 25.00%, average number of payments received November was 50.00%, and the average number of payments received in December was 15.00%. Do you average (25.00%, 50.00% and 15.00%) or do you have to go back to the numbers that calculated the averages. For example, October 25.00% was based on 25 payments being received out of a possible 100. So instead of taking the average of the averages, do you take the average payments and the average customers over the 3 months and calculate the average??? Answered by Harley Weston.
	A spotlight shines on a wall		2002-05-25
		From Barb: A spotlight on the ground shines on a wall 12m away. If a man 2m tall walks from the spotlight toward the bldg at a speed of 1.6 m/s, how fast is his shadow on the bldg decreasing when he is 4m from the bldg? Answered by Penny Nom.
	Conversion of units		2002-04-29
		From Matt: I am having trouble finding a workable equation for the following problem, particularly the conversion of two systems of measurement. The question states that there are 27 grams of salt in a kilogram of seawater. And it asks how many tonnes (1 tonne = 1000 kilograms) of salt are there in one cubic kilometer of ocean. It also says that the density of seawater is 1.1 g/cm3. What is the equation and how do I figure out how many kilograms there are in a cubic kilometre? Answered by Harley Weston.
	Percentage difference		2002-03-08
		From Tedd: Can you give me the formulas for calculating percentage differences between two numbers? For example: if the first number is 10 and the second number is 15, then the second number is 50% larger than the first number. However, the formula to calculate that percentage won't work if the first number is greater than the second number as in the following example: The first number is 15 and the second number is 10, with the second number being 33.3% less than the first number. Or maybe I'm mistaken and the same formula will work in both situations. Answered by Penny Nom.
	Why do you flip the inequality sign?		2001-10-26
		From Sean: I have a question about an inequality problem. Here it is: Solve and graph 5 - 3x => 17. (=> is greater than or equal). Please tell me why you flip the inequality sign when divinding by a negative number. Answered by Penny Nom.
	How far does the fly fly?		2001-08-07
		From Harold: 6 MPH 4 MPH Rachel ---------------------- Eli 10 Miles apart The fly is on Rachels handlebars. The fly is scared so it flys back and forth at 20 MP H. How far has the fly flown when Rachel and Eli meet? f Answered by Penny Nom.
	Jim's poker game		2001-05-24
		From Nick and Karnal: One day jim played poker with some of his friends and lost half his money.the number of dollars he had before the game was the same as the number of cents he had after the game, and the no of cents he had before the game was twice as much as the number of dollars he had after the game.how much money did he have before thegame??? Later that day jim met a friend Al on the street."hi al!Do u have any change on you al?""yes" "Good!can u give me a change of a dollar?" "I am afraid not!" "Then give me change of 50 cents.""I am sorry i cant." "how about a change of a quarter?""not possible." "a dime." "also not" "a nickel?" "not even that." al had no bills or silver dollars on him.whats the largest amount of cash he could have had? hope u can help me. Answered by Penny Nom.
	Coins and monomials		2001-03-04
		From A student: Tokola has 5 coins with a total value of $1.05. He canot make change for a dollar, 5 cents, 10 cents, 25 cent, or 50 cents. What 5 coins does he have? and Determine whether 6c-d is a monmial. Explain why or why not. Answered by Penny Nom.
	Velocity of a pendulum		2000-08-28
		From Mekca: A pendulum hangs from the ceiling. as the pendulum swings, its distance,d cm, form one wall of the room depends on the number of seconds,t, since it was set in motion. assume that the equation for d as a function of t is: d=80+30cos3.14/3t, t>0. estimate the instantaneous rate of change of d at t=5 by finding the average rates for t=5 to 5.1, t=5 to 5.01, and t=5 to 5.001. Answered by Harley Weston.
	Change for a dollar		2000-02-16
		From Rachelle: What is the least positive number of coins that is impossible to give out change for a dollar? It is higher than 50 i know and you can us dimes, nickels, pennies, quarters, 50 cent pieaces and silver dollars. Answered by Claude Tardif.
	Play ball		2000-02-03
		From Jessie: Here's a calc question that is probably a lot easier than I am making it. If you have a legendary "baseball problem" for the related rates section of Calc I, and you are given that the runner is running from 2nd to 3rd base at a given rate, and the umpire is standing at home plate, and you are given the distance between the bases on the field, how do you find the rate of change of the angle between the third base line (from the point of the umpire) and the runner? Here is a sample prob: Runner is moving from 2nd to 3rd base at a rate of 24 feet per second. Distance between the bases is 90 feet. What is the rate of change for the angle (theta, as described previously) when the runner is 30 feet from 3rd base? Answered by Harley Weston.
	Percentage change		1999-12-08
		From Michael Weinberg: I am the Laboratory information system supervisor in a hospital. Our computer system calculates the change of specific results to monitor a patient's status. But there is a problem with the calculation in the base code of the program. If one day the patient has a Blood count of 100 (P for Previous) then the next day the Blood count is 75 (C for current), the computer should calculate the change as -25% using the calculation |P-C|/P= D (D for Delta) and then check for positive or negative by the equation If P>C then D*-1 or If P The program is calculating using the equation: ((P/C)-1)*100 in the above situation this would calculate the Delta as 33.33333% Referenced in a Laboratory manual published before computers were used to calculate the delta changes. . . . Answered by Penny Nom.
	Percentage increase		1999-10-03
		From Ann Allen: I am a a student in the 12th grade. I need to know how to calclulate the following: A percentage increase from 2.0% to 9.5% is what percentage? Answered by Harley Weston.
	The average rate of change of a function		1999-04-20
		From Tammy: Suppose that the average rate of change of a function f over the interval from x=3 to x=3+h is given by 5e^h-4cos(2h). what is f'(3)? I would appreciate any help with this question. Answered by Harley Weston.

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