Topic: sum list of topics
start over

113 items are filed under this topic.

		Page 1/1

	Three numbers have a sum of 45		2020-05-06
		From Jayden: Three numbers have a sum of 45. The greatest of the 3 numbers is 2 greater than the least number. What are the numbers? * Answered by Penny Nom.
	Sigma notation		2019-12-04
		From Kenneth: What would be used for the top and bottom indices for the sigma sign in my example shown below? If the amounts were 1 + 2 + 3, the top index would be 3 and the bottom would be i = 1, but if the amounts are 1 + 2 + 4, or 1 + 0.05 + 1/3, what would the indices be since these amounts are in an uneven pattern. I thank you for your reply and explanation Answered by Harley Weston.
	The sum of the ages of Ruth and her mother is 77 years.		2019-11-06
		From Lydia: The sum of the ages of Ruth and her mother is 77 years. The difference in their ages is 27 years. How old is each? Answered by Penny Nom.
	How many numbers from the set have the sum of its digits equal to 2?		2019-10-24
		From Marcel: Hello. My question is the following: Given the set {1,2...........10exp2019}, how many numbers from the set have the sum of its digits equal to 2? I got some of them : 2 20 200 2000 20000 .......2. 10exp2018 11 110 1100 11000 110000....101 1010 10100 101000 1010000....10011 10010 100100 1001000 1010000.....10001 100010 1000100 10001000,,,,,,100001 1000010 10000100....... My problem is that I have difficulty in finding a strategy to obtain the exact quantity of numbers. Please help me, thanks Answered by Penny Nom.
	Four consecutive positive integers		2019-03-12
		From Nabila: The product of four consecutive positive integers in 24024 What is their sum? Answered by Penny Nom.
	A quadratic equation problem		2019-02-26
		From Em: One root of the equation 2x^2 + bx - 24 = 0 is -8. What are the possible values of b and the other root? Answered by Penny Nom.
	The sum and difference of two numbers		2018-08-30
		From Saranya: Hi, The question is to find the numbers from sum and difference. The Sum = 14 and the difference = 2 I found in this web site some useful answers. but my kid is going second grade only. She don't know how to do a division or multiplication. So can you please explain on how to find the answer using only the Addition and Subtraction. Thanks in advance. Answered by Penny Nom.
	The sum and difference of two numbers		2018-03-13
		From samima: Two numbers have a difference of 0.85 and the sum 1.What are the numbers? Answered by Penny Nom.
	The sum and difference of two numbers		2018-01-25
		From Ali: Hello, I was looking at the original question that was posted and answered by your team: http://mathcentral.uregina.ca/QQ/database/QQ.09.07/s/donna1.html I used the 7 and 4 as example and not looking for 39 per original question: A=7 B=4 7+ 4 =11 and 7-4 = 3 We end up with 11 +3 = 14 A= 14/2 give use 7 B = how do you solve for B or 4 with out knowing anything about 3 or any other numbers ? Thank you Ali Answered by Penny Nom.
	The sum and difference of two numbers		2017-03-20
		From Olivia: The sum of two numbers is 87 and their difference is 29. What are the two numbers Answered by Penny Nom.
	A road trip word problem		2016-04-10
		From Marc: While on a road trip I imagined this random word problem. Suppose I start a trip of 75 miles. My initial speed is 75 miles per hour. After every mile traveled I decrease my speed by one mile per hour. After the first mile I decrease my speed to 74 miles per hour and so on for each subsequent mile traveled. How long will it take to complete the 75 mile journey? Answered by Penny Nom.
	The integral of a sum		2016-03-10
		From Rahul: How to solve definite integral of a sum. The specific problem is as follows, Integral of ( 1+ sum of x^k, k=1 to k=n), x=0 to x=b *dx. The answer is b + sum of b^(k)/k, k=2, to k=n+1. I understand only the integral of first term. But integral of the sum I do not understand at all. Answered by Penny Nom.
	The sum of the angles of a triangle		2016-02-24
		From Sophia: Does every triangle add up to 180 degrees? (Such as a unique triangle) Answered by Penny Nom.
	Fractions of two quantities		2016-01-22
		From Melody: Kate ate 1/4 of her orange. Ben ate 2/4 of his banana. Did Kate and Ben eat 3/4 of theit fruit? Explain. Answered by Penny Nom.
	The sum of two repeating decimals		2015-10-22
		From Kaitlin: Here is the question I am struggling with: Is the sum of two repeating decimals always repeating decimal? Explain your answer and give an example. I answered this question thinking that no you cannot but only when adding 0.9 repeating, but my professor said this was incorrect. Thanks for the help! -Kaitlin Answered by Penny Nom.
	1 + 2 + 3 + ... + (2n - 1)		2015-01-01
		From Brian: Hi Maths Central My wife presented me with a query which may have a simple answer, but one that I can’t deduce or explain. Take the string of numbers, n=1,2,3,4,5… It seems that n(2n-1) = Sum((1…..(2n-1)) e.g. for n=5, both 5 x 9 and Sum(1….9) equal 45, and so on for other values of n. Could you please provide an explanation? Does it have an underlying reason and a name? Look forward to your response. Brian Answered by Penny Nom.
	Two quadratic polynomials		2014-10-28
		From khushboo: The zeroes of a quadratic polynomial x^2+ax+b are 'c' and 'd' and the zeroes of a quadratic polynomial x^2+cx+d=0 are 'a' and 'b'. find the numerical value of a+b+c+d where a, b, c and d are non zero integers. Answered by Penny Nom.
	The sum of two numbers is 52		2014-09-01
		From Blake: The sum of two numbers is 52 and the difference is 10. What are the numbers? i used to be real good at this stuff? Answered by Penny Nom.
	A price increase and a consumption decrease		2014-08-16
		From sujan: If the price of petrol increases by 25% and Rajesh intends to spend only 15% more on petrol then by how much % should he reduce the quantity of petrol he buys? Answered by Penny Nom.
	The combination of 6 numbers from 1 to 355 that gives us 360		2014-05-29
		From Ion: Hi, My name is Ion and I am trying to find the number of combinations of 6 numbers (angles) that would sum to 360 (degrees). Thank you! Answered by Robert Dawson.
	Two numbers whose difference is 16		2013-06-08
		From Johan: Two numbers whose difference is 16 and whose sum is 120 Answered by Penny Nom.
	1+2+4+8....= -1		2012-04-02
		From Andy: In this minutephysics video, it's claimed that 1+2+4+8....= -1 Is this true, and if so, how? < href="http://www.youtube.com/watch?v=kIq5CZlg8Rg">http://www.youtube.com/watch?v=kIq5CZlg8Rg Answered by Robert Dawson.
	Sum and difference of squares		2011-12-31
		From Anne: Se x e y são números reais distintos, então: a) (x^2 + y^2) / (x - y) = x + y b) (x^2 + y^2) / (x - y) = x - y c) (x^2 - y^2) / (x - y) = x + y d) (x^2 - y^2) / (x - y) = x - y e) Nenhuma das alternativas anteriores é verdadeira. Answered by Harley Weston.
	The sum of a series		2011-11-07
		From Rattanjeet: Find the sum of 1(1/2) + 2(1/4) + 3(1/6) + 4(1/6)(3/4) + 5(1/6)(3/4)2 + 6(1/6)(3/4)3+ ... where 1/6 + (1/6)(3/4) + (1/6)(3/4)2 + ... constitutes a geometric series. Answered by Penny Nom.
	4 + 10 + · · · + (6n − 2)		2010-04-21
		From Lan: Find the sum 4 + 10 + · · · + (6n − 2). The answer is 3(n^2) + n. How? Answered by Penny Nom.
	1/1+1/2+1/3...		2010-03-31
		From Mohd: you explained the way of getting the summation of 100 series numbers but what is the summation of the numbers 1/1+1/2+1/3+1/4+1/5.............................+1/100 Answered by Robert Dawson.
	1^3 + 2^3 + 3^3 +4^3 ... n^3 = ?		2010-01-29
		From ireimaima: Hi.. Can u please help me with this question.. I find that when i test eg: n=2 for n (n+1) /4, it seems that it does not giving me the right answer of 1^3 + 2^3 = 9 but 3/2... i'm confuse..can u please help me..thanks so much Prove that: 1^3 + 2^3 + 3^3 +4^3………………………………..n^3 = n (n+1) /4 Answered by Penny Nom.
	Odds and evens in an n by n+1 table		2010-01-21
		From Shankar: The boxes of an n * (n+1) table ( n rows and n+1 columns) are filled with integers. Prove that one can cross out several columns ( not all of them !) so that after this operation all the sums of the numbers in each row will be even. Answered by Robert Dawson.
	Summation Notation		2009-12-28
		From MANDIRA: I want to get the formula for expressing one number by summation of consucutive numbers . Answered by Janice Cotcher.
	Jill and Bill		2009-11-04
		From Lisa: Jill and Bill are two members of the Hill family. Jill is 8 years old and Bill is 9 years old. What will Bill's age be when the total of the digits in both their ages is once again 17? Answered by Stephen La Rocque.
	Arithmetic Sum & Sequence		2009-09-01
		From Alice: Find the 24th term of this sequence 6.8,8.0,9.2... Find the sum of the first 21 terms Answered by Janice Cotcher.
	The sum of the angles of a triangle		2009-05-18
		From mary: prove that the sum of the three angles inside any triangle always add up to 180 degrees? Answered by Harley Weston.
	The sum of the roots of a quartic		2009-04-21
		From dave: This is a algebra problem that i am confused about: The sum of the roots of x^4-x^3+5x^2+4=0 is: i tried graphing it, but it shows that there are no roots, but the answer is 1. are they wrong? Answered by Penny Nom.
	The sum of the roots of a quartic		2009-01-03
		From peter: How do you find the roots of an equation without graphing? like, i have a problem that says what is the sum of the roots of x^4-x^3+5x^2+4=0. Answered by Harley Weston.
	Determining the Unknown Numbers		2008-12-06
		From jacob: the sum of two numbers is 45 and their difference is 15. what are the two numbers? Answered by Janice Cotcher.
	The distribution of sample sums		2008-11-21
		From Mark: For large samples, the sample sum (Σ x) has an approximately normal distribution. The mean of the sample sum is n*μ and standard deviation is (σ*√n). The distribution of savings per account for savings and loan institution has a mean equal to $750 and a standard deviation equal to $25. For a sample of 50 such accounts, find the probability that the sum in the 50 accounts exceeds $38,000. Answered by Penny Nom.
	Factoring		2008-11-19
		From Neji: How do you factor (y-z) (y+z) (y^4+y^2z^2+z^4) and get (y+z)(y^2-yz+z^2) (y-z) (y^2+yz+z^2) as the answer? Answered by Harley Weston.
	Intercepts		2008-11-02
		From robert: What is the sum of the x-intercept and y-intercept of the line 3x-3y=24? Answered by Stephen La Rocque.
	An arithmetic series		2008-10-17
		From Laura: In an arithmetic series 5+9+13+...+tn has a sum of 945. How many terms does the series have? What formula do I use? Answered by Penny Nom.
	Factoring x^2 + 729		2008-08-19
		From peter: hello I,am having trouble factorising a polynomial into polynomial factors with real coefficients please can you help the polynomial is x^2+729 Answered by Harley Weston.
	Product of Two-Digit Numbers		2008-07-31
		From pete: The number 4641 can be expressed as the product of two two-digit whole numbers. What is the sum of these two numbers? Answered by Janice Cotcher.
	Sum and product of the roots of a quadratic		2008-07-03
		From Gautam: If a and b are the roots of x^2+px+1=0 and c and d are the roots of x^2+qx+1=0 prove that (a-c)(b-c)(a+d)(b+d)=q^2-p^2 Regards Gautam Answered by Harley Weston.
	The sum of the digits of two-digit number is 9		2008-07-01
		From Audrey: the sum of the digits of two-digit number is 9. if the digits are reversed, the new number if 63 greater than the original number. find the number. Answered by Penny Nom.
	111...111 * 2003		2008-06-23
		From Peggy: Number a = 111...111 formed by 2003 1's. Find the sum of the digits of the number 2003 * a. Answered by Penny Nom.
	The sum of the digits of a number		2008-06-23
		From Ben: Question: Using mathematical induction, prove that if the sum of the digits of a number is divisible by three, then the number itself is also divisible by 3. Answered by Penny Nom.
	The sum and product of the roots of a quadratic		2008-03-16
		From Katelyn: Write the quadratic equation.... Sum of the roots = 16 Product of the roots = -80 Answered by Penny Nom.
	Sum and difference of cubes		2008-01-30
		From Amanda: It has been a really long time since I was in Algebra and I can't remember how to factor cubes such as x^3 +81 or subtracting/adding fractions with variables such as [1/(x+h)+2]-[1/x+2]. Please help!!! Answered by Penny Nom.
	Total payments for a loan		2007-10-11
		From Robin: A person is going to arrange a loan at 3 mill. he will pay 150000 back each year , so it take 20 yrs. to finish. In addition he pays 5% interest of what is leaft each year. How do I find the sum-function which shows the total sum he have payed? Answered by Stephen La Rocque.
	Sum and difference of two mystery numbers		2007-10-04
		From Donna: The sum of two numbers is 39. The difference is 11. What are the numbers? Answered by Stephen La Rocque.
	T-totals		2007-09-26
		From Asma: I wanted to know what i should include in my T-totals maths coursework and also how i should lay out the coursework? Answered by Penny Nom.
	Period of a sum of trig functions		2007-06-17
		From Aakash: the period of the function f(x)=cos3x+sin4x+tan4x Answered by Stephen La Rocque.
	Buying topsoil		2007-05-16
		From Claudia: I am trying to figure out if it is cheaper to buy topsoil by the bag (one 40lbs bag for $1.66) or having it delivered for $60 for 4 cubic yards. Answered by Penny Nom.
	The sum of two numbers is 30		2006-11-03
		From GG: The sum of two numbers is 30 and the product of the same two numbers is 221. Find the two numbers. Answered by Stephen La Rocque.
	How does knowing the sum for 2+7 help you find the sum for 6+1		2006-10-26
		From Andrea: How does knowing the sum for 2+7 help you find the sum for 6+1 Answered by Haley Ess.
	The odd numbers from 30 to 80		2006-09-21
		From Kieran: If you added all the odd numbers from 30 to 80, would the answer be even or odd? Explain. I think it would be odd because I used this equation: (30 x 5)+(40 x 5)+(50 x 5)+(60 x 5)+(70 x 5)+(25 x 5)=1325 I used the numbers for each set of ten -30 to 80 times 5 and the amount of the endings-1,3,5,7,9- added, times 5. Is that right? Answered by Penny Nom.
	What is the sum of the first 100 whole numbers?		2006-05-31
		From Jo: what is the sum of the first 100 whole numbers? Answered by Natasha Glydon, Paul Betts and Penny Nom.
	Marine shipping - fuel consumption		2006-04-26
		From Sandy: When a ship is 800 nautical miles from port its speed is reduced by 20%, thereby reducing the daily fuel consumption by 42 tonnes and arriving in port with 50 tonnes onboard. If the fuel consumption per hour is given by the expression (0.136 + 0.001V^3) where V is speed in knots; Estimate a) reduced consumption per day b) fuel onboard when speed reduced c) normal consumption for 800 nautical mile voyage d) increase in steaming time Answered by Stephen La Rocque.
	Adding consecutive numbers		2006-04-26
		From Lisa: When I have a total that is the sum of consecutive numbers, how do I figure out what the numbers are? Answered by Stephen La Rocque.
	Proving a summation formula by induction		2006-04-19
		From Sharon: Prove by induction that the sum of all values 2^i from i=1 to n equals 2^(n+1) - 2 for n > 1. Answered by Stephen La Rocque.
	Arithmetic Sums		2006-04-12
		From Angel: (a) In a particular arithmetic sequence, u6 = 344.5 and u20 = 88.3. Find S28. (b) In a particular arithmetic series, S10 = 495 and S15 = 1005. Express S15 in sigma notation. Answered by Stephen La Rocque.
	Sum of a Geometric Sequence		2006-04-11
		From Andre: In a particular geometric sequence, U3=-3.6 and U10=12.9. Find S16 and S17. Answered by Stephen La Rocque.
	Factor		2006-03-08
		From Brad: Factor: x3 + 64m3 and 125p3 - q6 Answered by Penny Nom.
	Josh and John were both exposed to the flu		2005-12-16
		From Dudley: Josh and John were both exposed to the flu. John has a 25% chance of getting it, while Josh has a 75% chance of getting it. What are the chances that at least one of them has the flu? Answered by Penny Nom.
	Adding improper fractions		2005-11-25
		From Paula: I would like a simple step by step explanation on how to add improper fractions. Answered by Penny Nom.
	A block pyramid		2005-11-05
		From Kyle: if i make a block pyramid and it puts a new perimeter around it every time, for example the first layer will be 1 block across (area=1), the second layer will be 3 blocks across (area=9), the third layer will be 5 blocks across (area=15),etc. The normal block pyramid. I have figured out that in order to figure out the number of blocks needed for a certain level, the equation is (2x-1)2 or (2x-1)(2x-1), where x is equal to the level. For example, on the fourth level, the equation tells you that it will have an area of 49. How would i make an equation for the total number of blocks up to the level. For example, in order to complete 1 level you need 1 block, for 2 levels you need 10 blocks, for three levels you need 35 blocks, and for 4 levels you need 84 blocks. Answered by Penny Nom.
	A sum of 75 and a difference of 13		2005-10-30
		From Vicki: Find two numbers that have a difference of 13 AND A SUM OF 75? We need to learn about the formula or procedure. Answered by Penny Nom.
	What is the sum of the measures of the angles of a decagon?		2005-10-15
		From Dianna: What is the sum of the measures of the angles of a decagon? Answered by Penny Nom.
	Two groups that have equal sums		2005-09-30
		From Anita: using the numbers 1, 2, 3, 4, 5, 6, 7,and 8. how do we divide them into two groups so that they have equal sums? Answered by Penny.
	How to add three addends		2005-09-28
		From Patricia: explaination of how to add three addends if you use a double to add or if you use a sum of 10 8+3+2= 6+4+0= 3+3+6= 2+5+4= Answered by Baul Betts and Penny Nom.
	The sum of a series		2005-08-31
		From Aamod: Find the sum of the given series till n terms: (14\1*3) + (24\3*5) + (34\5*7)............... till n terms Answered by Chri Fisher.
	A set of numbers whose sum is 1		2005-07-21
		From Santos: Does there exist a set of numbers whose sum is 1, and the sum of whose squares is less than 0,01? Answered by Paul Betts.
	The sum of the digits of 2^100		2005-06-11
		From Richard: The sum of the digits was calculated for the number 2100, then the sum of the digits was calculated for the resulting number and so on, until a single digit is left. Answered by Penny Nom.
	Adding consecutive integers		2005-05-13
		From Yas: i need some help with my work which is to investigating sums of consecutive numbers for example: 15= 4+5+6 and 15=1+2+3+4+5 Answered by Penny Nom.
	Two matrix problems		2005-03-30
		From Sue: Question 1 Suppose all matrices in the equation below are square and invertible. Solve for x . BA-1XB-1 + 2BA + In = 0 (the symbol "0" here denotes the matrix of all 0's in it) Also, A-1 or B-1 is indicating inverse and "In" = for example, A-1 times A I hope you understand the above. I have to show all the steps. Question 2 Suppose we consider the set of all 2x2 matrices along with the operations of matrix addition and multiplication. Do they form a field? Why or why not? I think the answer is no because under multiplication it is not commutative and not all square matrices are invertible. I not positive so I'd like some help. Answered by Penny Nom.
	A product equals a sum		2005-03-27
		From Tor: Can you please help me with a general formula for the following system: 2+2=2*2 3+3/2=3*3/2 4+4/3=4*4/3 and how will you prove the formula? Answered by Penny Nom.
	The sum of the digits		2005-03-16
		From kelsey: What is the sum of the digits in the decimal form of 21999 * 52002? Answered by Claude Tardif.
	A matrix construction problem		2005-03-14
		From Marcelo: I want to know if is it possible to solve this problem: I have an empty NxM matrix and I know totals (sum) by rows and totals by column. Is there any algorithm to fill the matrix so that the summary of columns and rows gives the original values I have? Answered by Harley Weston.
	Sum to n terms of the series i.(2^(n-i))		2005-01-28
		From Satya: Sum to n terms of the series i.(2n-i) Answered by Penny Nom.
	1+3+5+...+(2n+1)		2004-09-10
		From Emma: Prove that 1+3+5+...+(2n+1)= (n+1)2 Answered by Penny Nom.
	Factoring		2004-07-19
		From A student: Factor completely: 3x3 - 24y3 54x6 + 16y3 16xy - 4x - 4y - 1 0.09x2 - 0.16y2 Answered by Penny Nom.
	The sum of some positive integers		2004-06-07
		From A student: Find the sum of all positive integers not greater than 10000 that are divisible by neither 3 nor 7. Answered by Penny Nom.
	The sum of 4,0,-4..., -156		2004-04-28
		From Christina: find the requested sum of the arithmetic sequence 4,0,-4..., -156 Answered by Penny Nom.
	Factoring		2004-04-27
		From Bipin: FACTORISE: a to the power of 6 + b to the power of 6 Answered by Penny Nom.
	Some factoring problems		2004-04-15
		From KJ: Factor these: x3+125 -----> (x+5)3 8x3-27 -----> (?) x2+36 -----> (x+6)2 x4-5x2+4 --> (?) Answered by Penny Nom.
	Sum of the angles in a pentagon		2004-03-11
		From Ashish: What is the sum of all the measures of the angles of a Pentagon Answered by Penny Nom.
	Sums and differences		2004-02-10
		From David: The sum of two whole numbers is 63. The difference between the numbers is 10. Find all the possible pairs. Answered by Claude Tardif and Penny Nom.
	The sum of two numbers is 5 and their difference is		2003-06-16
		From Akhil: The sum of two numbers is 5 and their difference is 11. What is the product of the two numbers? Answered by Penny Nom.
	positive multiples of 10 that are the sum of four consecutive integers		2003-05-01
		From Taurus: How many positive multiples of 10 that are less than 1000 are the sum of four consecutive integers? Answered by Penny Nom.
	Three digit number		2003-03-10
		From Grace: What three digit positive integer is exactly 32 times the sum of its digits? Answered by Claude Tardif.
	Factoring		2002-12-11
		From Larry: Question: how do u factor trinonmials EX: X 3 + Y 3 X 3 - 8Y 3 8X 2 - 72 64A 3 - 125B 6 Answered by Penny Nom.
	Factor completely		2002-11-21
		From Shelley: these two questions are to be factored completely but i have no idea how to factor them (x-4y) 2 - 3(x-4y) - 4 x 6 + y 6 Answered by Penny Nom.
	Fuel consumption		2002-11-11
		From Guy: When a car is driven 'normally' the feul consumption is 7.5 per litres per 100km. On a particular journey the car was driven in 'hard' and the consumption changed to 9.1 litres per 100km. Fuel cost 80p per litre. Calculate: a) The extra feul consumed. b) The extra cost of feul, in pounds, for the journey when the car was driven in 'hard'. Answered by Penny Nom.
	Sums of evens		2002-09-14
		From Rosa: How do I find a geometric way to easily compute sums of consecutive even numbers 2 + 4 + 6 + .... Answered by Leeanne Boehm and Harley Weston.
	7+8+9+...+1000		2002-09-11
		From Shirley: My question is what is the formula for adding up numbers when you don't start with number 1? For example 3 + 4 + 5 + 6 = 18. But how could you arrive at the answer without adding all the numbers? Answered by Penny Nom.
	The sum of the first one hundred even numbers		2002-09-10
		From Arthur: What is the sum of the first one hundred even numbers? Answered by Penny Nom.
	The sum of the areas of two regular decagons		2002-05-27
		From A parent: The sum of the areas of two regular decagons is 39 square inches, and their radii are in the ratio of 2:3. Find the area of the larger decagon. Answered by Paul Betts.
	Arithmetic progressions		2002-04-24
		From David: I have been searching everywhere for the formula to mathamatical progression. Answered by Penny Nom.
	24x^4 + 3x		2002-03-18
		From gary: 24x 4 + 3x Answered by Penny Nom.
	1+2+3+...+1000		2001-10-01
		From Louise: Find a quick way to add all Intergers (whole Numbers) between 1 and 1000? Answered by Walter Whiteley.
	Conservation, consumption and population growth		2001-06-04
		From Steve: I'm trying to quantify the relation between conservation/consumption and population growth. For instance let's consider California: The 2000 census states that California's population grew from 29,760* in 4-1990 to 33,871 in 4-2000. I want to find r or rate of growth per year. Based on the exponential growth formula for population growth: . . . Answered by Penny Nom.
	Marginal Propensity to Consume		2001-05-09
		From Esther: The derivative of the national consumption function C = f(y) is called the ____________________. Answered by Judi McDonald.
	National consumption function		2001-05-09
		From Brian: If consumption is $11 billion when disposable income is 0 and the marginal propensity to consume is dC/dy = 1/(2y+4)1/2+0.3(in billions of dollars), find the national consumption function. Answered by Harley Weston.
	Sigma		2001-03-31
		From A student: What does the Sigma symbol mean in mathematics? Answered by Penny Nom.
	The sum of all ten-digit numbers.		2001-01-10
		From John: Compute the sum of all ten-digit numbers. Can you determine the sum of all n -digit numbers? Answered by Sukanta Pati.
	A dollar, quarter, dime, nickle and penny		2001-01-07
		From Sarah: Arnold has a dollar coin, one dime, one quarter, one nickel, and a penny. The number of different sums of money that can be formed using three coins is... Answered by Penny Nom.
	Infinite Geometric Series		2000-11-10
		From Sam Carter: I ran into a problem when studying how to find the sum of an infinite geometric series. My math book attempts to explain the concept by giving formulas involving sigma and |r|, but it does not really explain how to go about finding the sum of an infinite geometric series. If you could either help me with this or point me in the direction of an informative website that could help me, I'd appreciate it. Answered by Harley Weston.
	The sum of the cubes is the square of the sum		2000-10-10
		From Otoniel: Without using mathematical induction, or any other method discovered after 1010 a.d. , prove that the sum of i3, (where i, is the index of summation) from one to, n, is equal to ((n*(n+1))/2)2 Answered by Penny Nom.
	1 + 2 + 3 + ... + 50		2000-09-14
		From Vicki Charron: How can you calculate the total of the numbers one through fifty, without adding up the individual numbers? Answered by Penny Nom.
	The sum of the squares of 13 consecutive positive integers		2000-08-25
		From Wallace: Prove that it is not possible to have the sum of the squares of 13 consecutive positive integers be a square. Answered by Harley Weston.
	Riemann sums		2000-03-30
		From Joshua D. Parham: If n is a positive integer, then lim (1/n)[1/(1+1/n) + 1/(1+(2/n) + ... + 1/(1+n/n)] n->infinity can be expressed as the integral from 1 to 2 of 1/x dx Answered by Penny Nom.
	The sum of the cubes is the square of the sum		1999-08-25
		From Bernard Yuen: How to prove 13 + 23 + 33 + 43 + ... n3 is equal to (1+2+3+...n)2? (for n is positive integer) Answered by Harley Weston.
	Compound Interest		1999-07-01
		From Kim Palmer: In early 1997, my son borrowed $4831 at 7.5%. He has made 30 monthly payments of $130 each. He is now in a position to pay off the balance. What is his remaining principal? Answered by Penny Nom.
	Factoring		1999-03-30
		From Maggie Stephens: I don't know anything about factoring would you plese help me. 3x4 - 48 54x6 + 16y3 125-8x3 12x2 - 36x + 27 9 - 81x2 a3 + b3c3 I would greatly appreciate any help you can give me thanks. Answered by Jack LeSage.

		Page 1/1