







The tens digit of a number is five times the unit digit 
20160519 

From sanjeev: The tens digit of a number is five times the unit digit. Find the number? Answered by Penny Nom. 





Four equations in 3 unknowns 
20150823 

From damien: solve:
S x U  T = 44
T  U x S = 36
U + T  S = 7
U x U / S = 4 Answered by Penny Nom. 





A two digit number 
20150821 

From Cameron: Write the 2 digit number that matches the clues.
My number has a tens digit that is 8 more than the ones digit. Zero is not one of my digits.
My number is ________. Answered by Penny Nom. 





A tennis ball in a triangular prism 
20141006 

From Anna: Hi, I need to find the the base and the height of a triangular prism, but I only know the diameter of a tennis ball that fits exactly in the triangular container.. The diameter for the ball is 8.50cm.
Can you help me find the formula?
Thank you! Answered by Penny Nom. 





What are the possible lengths of the hypotenuse? 
20140307 

From audrey: The three sides of a right angles triangle measure x2, x+5, and 2x1 in length.
What are the possible lengths of the hypotenuse?
... I'm doing the equation c2=a2+b2 and subbing in the numbers but nothing makes sense Answered by Penny Nom. 





The hypotenuse 
20120906 

From Jeevan: how can i find the height and base of a right angle triangle if i have the hypotenuse only ? Answered by Penny Nom. 





Three tennis balls 
20120517 

From eiman: Three tennis balls are placed inside a container . the tennis balls are tangent to the top, bottom,and sides of the container . find the volume of air inside the container surrounding the tennis balls if the diameter of the tennis balls is 6 inches Answered by Chris Fisher. 





The dimensions of a conical tent 
20120304 

From yash: a conical tent is to accommodate 11 people.Each person must have 4m square of space on the ground and 20m cube at air to breathe.Find the height and radius of the conical tent.26202 Answered by Penny Nom. 





Figures with dots 
20120215 

From A: Okay so my daughter came home and had this question for homework from her teacher. I have no idea what it means HELP!!
The question shows a figure that is a square. It has 5 dots on the top, bottom and on the sides looks similar to this:
. . . . .
. .
. .
. .
. . . . .
they want to know 3 more ways to show the number of dots in the figure. They have already shown one with just counting them
and the other one that they showed was circling the four corner dots and then taking the dots in between with a number sentence set up
like this: 4+4*(52) = 4+4*3= 16. They also besides giving 3 ways want us to write a number sentence and an algebraic sentence to show the number of
dots in the figure with "n" sides. Please help! So confusing ! I don't know if my square turned out or not but it should be 5 across the top and bottom and
on the sides and no dots in teh middle it is just the outside. Answered by Penny Nom. 





Ten percentage of 24 hours 
20120123 

From robin: Hai.. Myself Robin.. May i know the ten percentage of 24 hours? Pls help me.. Thank you. Answered by Penny Nom. 





Extended real numbers 
20111212 

From Justin: Hi there, I was wondering does +infinity=+infinity in the extended real number system? Basically, I was wondering does +infinity=+infinity since infinity and any extended real number (except +infinity) are less than +infinity?
Sincerely,
Justin Answered by Robert Dawson. 





Expanded form 
20111012 

From Chris: Write this number in expanded form
4 326 180 501
Thanks!!! Answered by Penny Nom. 





Tennis schedule 
20110404 

From Toni: I need to create a doubles tennis schedule for 6 players
playing over a 32 week schedule where no player
repeats with a partner. Answered by Victoria West. 





A two digit number 
20110301 

From jhoanna: the sum of the digits of a two digit number is 10. The value of the number is 16 times the units digit.Find the number. Answered by Penny Nom. 





Cutting the top off a conical tent 
20110222 

From tom: how far from the top must you cut a conical tent in order to cut the
cloth in half... Answered by Penny Nom. 





A division sentence for an array 
20101005 

From Laura: On a math test Grace needs to look at an array and write a division sentence for the array. Grace writes 18/3=6 on her answer sheet. Describe what the array on Graces test looks like. Answered by Penny Nom. 





A play tent 
20100628 

From Susan: Hi!!!
I am making a play tent as seen at the link below and need to figure out how to get the dimensions for the cone shape. The one shown has 4 different seams, but I guess I can get away with just one seam to sew it together (?) I need it to go over a hula hoop as that is what I am using for the round support at the top. My hula hoop is
35" in diameter from outside edge to outside edge. I would like the height of the teepee to be around 30" from the center to the peak.
Thanks so much, oh my gosh, I have been fretting for 2 days about this and my hair is about to fall out!!!!
Please contact me if you need any additional info.
~Susan
http://www.landofnod.com/family.aspx?c=52&f=4100 Answered by Penny Nom. 





The hypotenuse of a triangle 
20100522 

From linda: find the length of the hypotenuse of a triangle with legs of 12in. and 17in. round to the nearest hundredth Answered by Tyler Wood. 





The hypotenuse 
20100227 

From Dannielle: how do you find the hypotenuse if a=8 and b=6? Answered by Penny Nom. 





A square corner 
20100211 

From Trevor: I am building a new house and wish to set it out on site with the use of
profile boards and string. I want to be certain it is correct in terms of
squareness. I have a vague idea that the square on the hypotenuse should
be equal to the sum of the squares of the other two sides.
I get a little lost here and need some help. The building is a rectangle
measuring 40x30 feet to exterior brickwork. I guess that the length
of the hypotenuse should be exactly the square root of the combined
squares of the two sides.
Using the above measurements could you give me calculations from nuts
to soup as to the correct length of the diagonal. And what adjustments
are needed if everthing is not in accord.
Trevor. Answered by Robert Dawson. 





The extended real numbers 
20091102 

From Justin: Hello there, I was wondering is the set of extended real numbers a closed set or an open set?
Justin Answered by Robert Dawson. 





The hypotenuse of a right triangle 
20091018 

From steven: the perimeter of a right triangle is 20 cm. its area is 15 sq cm. find its hypotenuse. Answered by Penny Nom. 





The extended real number system 
20090630 

From Justin: Hi again, thanks a lot for answering my previous question! I was also just wondering again if the extended real number system has a potential or actual infinity because it includes positive infinity as a point that exists at the end of it?
All the Best,
Justin Answered by Robert Dawson. 





Potential infinity and actual infinity 
20090629 

From Justin: Hi there, I was just wondering what is the difference between the potential infinity and actual infinity in math? Thanks a lot for your help with this question!
All the Best,
Justin Answered by Robert Dawson. 





Is one Infinity larger than another in the extended real number system? 
20090624 

From Justin: Hello there, I was wondering if one infinity is larger than another in the extended real number system (just like in the transfinite ordinals and cardinals with respect to infinite sets) or are all infinities the same size in the extended real number system? Thanks sooo much for answering my question! I greatly appreciate it!
All the Best,
Justin Answered by Robert Dawson. 





An array with 2 more rows than columns 
20090228 

From Mario: Write a division sentence modeled by an array that has 2 more rows than the number in each row. Answered by Penny Nom. 





Augmented matrix: independent, dependent, or inconsistent? 
20090223 

From Anna: Perform row operations on the augmented matrix as far as necessary to determine whether the system is independent, dependent, or inconsistent.
x + y + z = 11
x  y + 3z = 5
2x + 2y + 2z = 15 Answered by Harley Weston. 





A tennis schedule 
20090126 

From Lorraine: I need to create a tennis schedule. We have 8 players, but only 4 play at one time. I need to create a schedule for 34 matches, but of the 34 each player plays 17 times. Each player must also play with each of the other 7 the same number of times. For instance player 1 will play 17 times, and will play with the other players the same number of times as player 2 does. Is this even possible? Answered by Robert Dawson. 





The tens digit of 0! + 1! + 2! + 3! + 4! .............+9999! + 10000! 
20090123 

From Kaylyn: determine the tens digit for the expression:
0! + 1! + 2! + 3! + 4! .............+9999! + 10000! Answered by Robert Dawson and Penny Nom. 





The third vertex of a right triangle 
20081210 

From prashant: how to calculate coordinates of third vertex in a right angle triangle given the coordinates of hypotenuse as (1,3) and (4,1) Answered by Robert Dawson. 





The part before the repetend 
20081102 

From Puerto: Hello,
I teach mathematics in a bilingual programme using English. I have learned that the group of digits that repeat in a repeating decimal is called repetend but i need to know how are called the previous ones when the decimal is a delayedrepeating one. I mean, in 0.34555555 5 is the repetend, the period is one and...how are called 34?
Thanks in advance. Answered by Stephen La Rocque and Penny Nom. 





A falling block 
20081018 

From KOBINA: A 50 kg block being held at rest 20m above the ground is released. the block falls (no friction). how fast is the block traveling (in m/sec) when it has lost 40% of its original potential energy. Answered by Stephen La Rocque. 





Repeating fractions 
20080909 

From Juli: My teacher recently put my math class to the test...
We were deiscussing repeating fractions and she asked
us to find out what the bar over a repeating decimal is called. I found out
it was called the vinculum. But she also said to find out what the number
under the vinculum was called. I can't seem to find it anywhere. Answered by Penny Nom. 





How do you write 92 tenths as a decimal? 
20080905 

From Miriam: How do you write 92 tenths as a decimal? Answered by Penny Nom. 





Ten acres 
20080525 

From RICHARD: hi, i am getting 10 acres of ground from a aunt which is going to be taken out of a 50 acre tract.both the north and south lines are 1320 feet long.i need to know how long the east and west lines will be to make the 10 acres and what the square footage will be for the 10 acres Answered by Harley Weston. 





Girls, cats and kittens 
20080516 

From leria: There are 7 girls in a bus.
Each girl has 7 backpacks
In each backpack, there are 7 big cats
For every big cat, there are 7 little cats.
How many legs are there in the bus? One hint? it's a 6 digit number Answered by Penny Nom. 





A solid figure with 3 rectangular faces and 2 triangular faces 
20080417 

From Emily: I am in the 3rd grade and my teacher gave us a question. What is a
solid figure with 3 rectangular faces and 2 triangular faces? Answered by Penny Nom. 





Women, cats and kittens 
20080212 

From Paige: There are 7 women on a bus. Each has a backpack. In each backpack there are seven cats. Each cat has seven kittens. How many legs are there total on the bus? Answered by Penny Nom. 





A 454590 triangle 
20071213 

From Aaditya: explain to me please how to do the 454590 theorem when one of the legs(not the
hypotenuse) is 3. How do you find the remaining two sides? please help me out. Answered by Leeanne Boehm. 





A right triangle 
20071206 

From Shubhomoy: The coordinates of a hypotenuse are (1,3) and (4,1). Find the equations of the perpendicular sides. Answered by Harley Weston. 





A right triangle 
20071121 

From Jason: One leg of a right triangle is 12 inches long. The other leg is 3 inches
shorter than the hypotenuse. Find the lenght of the hypotenuse. Answered by Penny Nom. 





A ten digit number 
20071111 

From jeff: find the greatest tendigit positive multiple of 12 using each digit once and only once Answered by Penny Nom. 





Area and side length of a hexagonal tent 
20071009 

From Mark: Trying to buy a tent with 6 sides, in the catalog they give me sq. ft., what is the distance from side to side of a hexagonal tent with an area of 90 sq. ft. Answered by Stephen La Rocque. 





How many ten thousands makes one million? 
20071002 

From Payton: how many ten thousands makes one million? Answered by Penny Nom. 





The hypotenuse 
20070920 

From Kasey: What is the hypotenuse of 96 squared and 108 squared? Answered by Penny Nom. 





Tens and ones 
20070916 

From julia: My son has come home with a math question "what i know about 10s and 1s" we're totally stumped any information you can provide would be greatly appreciated Answered by Harley Weston. 





Number sentences 
20070915 

From jen: list the addition number sentences that can be written using two sets of cards with the numbers 5 6 and 7. which number sentences have the same addends but show a different order?,,,,,,,,,,,,,,Ithis is for my son in 3rd grade and for the life of us we can't figure it out,,thanks for this elementary help Answered by Harley Weston. 





The tens digit 
20070821 

From Arul: Hi..
Please help me on this question..
Sequence 2, 7, 22,…after the first three terms, each term is three times the previous term plus 1, a(n+1)=3an + 1. What is the sum of tens digit 33rd and tens digit of the 35 term? Answered by Penny Nom. 





The tension in a single strand of wire 
20070813 

From Gene: Seeking an equation that calculates the tension in a single strand of wire or rope. Conditions: the wire is fixed at both ends, A known weight is suspended from the center of the span. The weight will dipslace the strand downward some distance Y. Let the distance between the fixed ends be X= 500mm. Weight W=0.5kg. Original tension in the strand is T= 10 newtons.Your help sincerely appreciated. Answered by Gabriel Potter and Stephen La Rocque. 





A right triangle 
20070811 

From Peter: Ok, is it possible to find the height and base of a right triangle when all the information you are given is the length of the hypotenuse?
I also know that the angle between side b and the hypotenuse is 45 degrees. please help. Answered by Walter Whiteley. 





Height of an antenna (angle of elevation) 
20070716 

From Fhay: An antenna stands on the edge of the top of a 52 story building from a point 320 ft. from the base of the building, the angle of elevation to the top of the antenna is 64 degrees in each story is 12 ft. high. Find the height of the antenna Answered by Stephen La Rocque. 





Grams of vodka 
20070710 

From Andrew: milliliters to grams..vodka 80 proof? Answered by Stephen La Rocque. 





Dried grapes and percentage of water content 
20070709 

From Jyoti: Fresh grapes contain 90% water by weight while dried grapes contain 20 % water by weight. what will be the weight of dry graprs available from 20kg of fresh grapes? Answered by Stephen La Rocque. 





Finding the hypotenuse without Pythagorus 
20070511 

From Shelbie: How do i find the hypotenuse of a right traingle not using the pythagorean thereom if i have the measurements of the legs? Answered by Stephen La Rocque. 





Hypotenuse 
20070503 

From ashley: how do you find the hypotenuse Answered by Penny Nom. 





Pythagoras was right 
20070411 

From Vineet: in a right angle triangle, hypotenuse side is less than the sum of other two
sides, how the square of hypotenuse is equal to the sum of squares of other two sides? Answered by Stephen La Rocque. 





What is the hypotenuse of a right traingle 
20070404 

From debbie: what is the hypotenuse of a right triangle with sides of 38 meters and 24.2 meters. Answered by Stephen La Rocque. 





Algebra 
20070403 

From Emily: 9,365 and 2,242 added to the difference between 255 and half of a number is 11,784. What is the number? Answered by Haley Ess. 





What is the intensity 5m below the surface? 
20070331 

From david: I have this question which I am supposed to set it up and solve as a differential equation. I know how to solve the diffrential equation but I am having hard time understanding this question. Here is the question: The intensity of light in the ocean decreases the deeper you dive. In fact, the rate at which the intensity decreases is proportional to the current intensity. Setup the corresponding differential equation and solve for I(Y), the intensity I as a function of current intensity Y. If the light intensity 2m below the surface is 25% of the intensity at the surface, what is the intensity 5m below the surface. Can you please explain to me what does it mean by current intensity and how do I set this equation up. Thanks for the help. Answered by Penny Nom. 





The tens digit of a really large number 
20070305 

From Sai: How can i find the tens digit of a really large number? i was gven 63^15 + 15^63 in a competitive exam. Answered by Penny Nom. 





A gymnast is swinging on a high bar. 
20070214 

From William: A gymnast is swinging on a high bar. The distance between his waist (center of mass) and the bar is 1.1 m. If his speed at the top of his swing is zero and his gain in speed is due entirely to his change in gravitational potential energy, find his speed at the bottom of his swing. Answered by Stephen La Rocque. 





The hypotenuse 
20061002 

From Ashley: How do you find the hypotenuse of a right triangle? I don't understand how to find c. Answered by Stephen La Rocque. 





Volume of a tennis ball can 
20060416 

From Jon: Tennis balls are generally packaged in circular cylinders that hold 3 balls each. The diameter of a tennis ball is 6.5 cm. Find the volume of a can of tennis balls. Answered by Stephen La Rocque. 





An array problem 
20060131 

From Cynthia:
Write a number sentence for this array........
It's a rectangle box 3 down and 4 wide.
Answered by Penny Nom. 





Percentage increase in sound intensity 
20060129 

From David: I am doing some emotion response mapping.
Being a composer I know how to push the heart beat tempo by a % increase of BPM in my music. I want to know how to calculate an increase in intensity of sound. Now I have 60 decibels. I want an increase of intensity by a factor n% with out going over 156 decibels.
Answered by Penny Nom. 





how can i find the height of a triangle if i have the base and the hypotenuse 
20060127 

From Kelsey: how can i find the height of a triangle if i have the base and the hypotenuse Answered by Penny Nom. 





I want to place four sticks equal distance apart into a tennis ball. 
20051213 

From Bev: I want to place four sticks equal distance apart into a 3 inch tennis ball. The circumference of the ball is 9 inches. Where should I place the sticks and how many inches apart. Answered by Chris Fisher. 





A television antenna sits on a roof. 
20050730 

From Liz: A television antenna sits on a roof. Two 76foot guy wires are positioned on opposite sides of the antenna. The angle of elevation each makes with the ground is 24 degrees. How far apart are the ends of the two guys wires? Answered by Penny Nom. 





If the distance of a person from a tower is 100 m... 
20050215 

From Agustin: If the distance of a person from a tower is 100 m and the angle subtended by the top of the tower with the ground is 30 degrees, what is the height of the tower in meters?
Answered by Harley Weston. 





Tennis balls and probability 
20041101 

From Jeremy: I have a hopper of tennis balls that contains 25 new tennis balls and 10 old tennis balls. In the hopper the tennis balls are mixed up randomly. If i take one ball out of the hopper and hit it and then put it back and then take another ball out of the hopper and hit it and put it back, what is the probability that i hit two new tennis balls? Also a tennis ball becomes old after being hit just once. Answered by Penny Nom. 





The hypotenuse of a right triangle 
20040920 

From Shannon: I am trying to find the hypotenuse of a right triangle with only the length of the opposite side. What is the formula as I don't have the length of the adjacent side? Can I compute it without knowing what the other two angles are? Answered by Penny Nom. 





The length of a cut 
20040917 

From Florita: My daughhter, who is a 9th grader is attempting to cut a piece of wood after determining the length of the cut for the hypotenuse. These are the measures:
a=4squared, b=6squared.
She determined that c should equal 52. But when she measured the actual piece to be cut, c measured 39.5 inches! Can you offer any insight as to what she is doing wrong? I have suggested that she may be working with an Acute rather than a Right angle . But she insists that it is a Right angle after using a "framing square". Answered by Claude Tardif. 





X bar 
20031104 

From mary: Remind me what this means:
_
X
Answered by Andrei Volodin. 





10,000 
20031008 

From Nathan: what two numbers make the product of 10,000. Neither number can end in a zero Answered by Penny Nom. 





The digits in 349 
20030912 

From Franik: in the number 349, which number has the least value, and why? Answered by Penny Nom. 





Converting from base 10 to base 5 
20030910 

From Susy:
My son, who is 9 in grade 5 has been asked to convert base 10 numerals into base 5. His first question of: 24(10) he has calculated to be 4x5 + 4x1 = 44 (5) The next question however is the tricky one.Ý We know the answer is supposed to be 100 but we find it difficult to get this in the way he understands it. 25 (10) = _________________ 100 (5) Can you help us figure out how we reach the answer. Answered by Claude Tardif and Penny Nom. 





Converting to base 10 
20030828 

From Karen: My son is in 5th grade.Ý He is learning how to convert numbers from base 2 to base 10, and base 5 to base 10.Ý Can you explain it to me in the simplest terms? Answered by Penny Nom. 





Round to hundredths 
20021119 

From Brittany: Can u tell me how to do a problem like this:
35 divded by 4.8= Round to hundreths. Answered by Penny Nom. 





oneths 
20020430 

From Logan: why are there tenstenths hundredshudreths, but not oneths if that made no sense then how about this why does everything have two ways of saying things like tens and tenths but not a oneths Answered by Claude Tardif. 





Catenary 
20020102 

From Jason: I am a high school math teacher. I was asked by a friend who is in architectural design for a method for determining the volume of what he called a Catenary. The Catenary curve is modeled by the equation y=a cosh(x/a). I ran into a mess when I tried to compute the volume of the solid formed by revolving that curve around the yaxis. Any help you can provide would be greatly appreciated. Answered by Harley Weston. 





Tenths, hundredths, and thousandths 
20011017 

From Cheri: I would like the French terms for the decimal place values of tenths, hundredths, and thousandths. (I would be interested in the Spanish terms also if you had them.) Answered by Maria Torres and Claude Tardif. 





The repetend in repeating decimals 
20010321 

From Sharon: What is the name for the bar over the repetend in repeating decimals? Also, what is the name of the long division "house"? Answered by Penny Nom. 





The hypotenuse of a right triangle 
20010122 

From Phillipe: How do you find the hypotenuse of a right triangle? Answered by Penny Nom. 





The sum of all tendigit numbers. 
20010110 

From John: Compute the sum of all tendigit numbers. Can you determine the sum of all n digit numbers? Answered by Sukanta Pati. 





Static electricity on an airplane 
20001112 

From John: What discharges an airplane of static electricity in a electric storm when it is flying. I assume the charge is on the out side of the plane but when does it get discharged, or does it occur at landing? Answered by Ted Mathie. 





Lobbing a tennis ball 
20001031 

From Alex: If a tennis ball is lobbed into the air with an initial upward velocity of 12 meters per second, its velocity and height will be functions of time in flight described by the following rules: V=129.8T and H=1+12T4.9T^{ 2} Find the maximum height of the tennis ball and the time it takes to reach that height. Answered by Penny Nom. 





Ten stools 
20000206 

From Haim: In a cafe with ten stools, three customers want to be seated, so that no two are next to each other. How many ways can this be done? Do not consider it to be a separate seating if two customers switch seats. Answered by Denis Hanson and Walter Whiteley. 





Tennis doubles 
20000204 

From Brittany Allinson: Cheri, Beth and Jacinta are daughters of Mr. Sullivan, Mr. Marchand, and Mr. Benoit. Four of these people are playing tennis doubles. Mr. Benoit's daughter and Mr. Sullivan are partners. Cheri's father and Mr. Marchand's daughter are also partners. There aren't any father/daughter combinations. Who is Cheri's father? Answered by Penny Nom. 





0! + 1! + 2! + 3! + ... + 2000! 
19991021 

From Melissa: My name is melissa. I am a 9th grade student I am having trouble finding out how to do this: What is the tens digit of 0! + 1! + 2! + 3! + ... + 2000! I know how to find these, but my calculator cant go any higher than 69! Is there any way i can do this problem? Answered by Penny Nom. 





Measuring the fourth dimension 
19990607 

From Suzanne Hall: Hi! The other day, two of my students asked a very interesting question: Is the fourth dimension measured with hypercubes? Their reasoning went like this: Lines are 1D and are measured with line segments, which are part of a line. Planes are 2D and are measured with squares, which are part of a plane. Space is 3D and is measured with cubes, which are part of space. So, logically, hypercubes would be used to measure the fourth dimension. Answered by Chris Fisher. 





Place Value 
19990105 

From Reg: I work in a Section 27 classroom with various grades. I am looking for assistance on how to deliver a lesson on place value:decimal numbers keeping in mind that they need to see it (visual) to comprehend. I am looking for grade 46 level. Answered by Jack LeSage. 





il y a deux contenant 
20070123 

From Eric: il y a deux contenant un de 3 litre et un de 5 litre les deux sont vide comment en les remplisant on peux obtenire 4 litre Answered by Claude Tardif. 





isomorphisme 
20000810 

From Romain Kroes: Pour les beoins d'un ouvrage d'économie que je suis en train de terminer, pouvezvous me dire qui est (sont) l'inventeur de l' "isomorphisme" en mathématiques (calcul tensoriel)? Answered by Claude Tardif. 

