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Can the standard deviation ever = 0? |
2002-02-16 |
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From Karen:
If given a class of 30 people who take a test with a mean of 80. Can the standard deviation ever = 0? If so, why?
Answered by Penny Nom. |
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Diameter of a pipe |
2002-02-16 |
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From Landry:
I am trying to calculate the dia. of a pipe 60 inches long that will hold a gallon of water. What is the formula?
Answered by Penny Nom. |
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The perimeter of an ellipse |
2002-02-14 |
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From Harry:
I am planning to build a coffe table with an ellipse of 24x36 for the top. I wish to decorate the edge and need to know the lenght of the perimeter for lay out purposes. Is there an easy way to approximate this figure with out using intergal calculus?
Answered by Penny Nom. |
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Nets for pyramids |
2002-02-14 |
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From Michelle:
I want to have my students create nets for pyramids and I need to know how to find the correct range of degrees for the interior congruent angles of the isosceles triangular faces. For example, I know for a square-based pyramid that 77 degrees will work; however, I know other angle measures will also work. I'm just not sure how to find the minimum degree measure to have the net actually "work". I'm assuming the maximum would be 89 degrees, although that would make for a very tall pyramid.
Answered by Penny Nom. |
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36 is 20% less than _____? |
2002-02-13 |
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From Lori:
36 is 20% less than _____?
Answered by Walter Whiteley. |
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A man and his wife walk up a moving escalator |
2002-02-13 |
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From Monty:
A man and his wife walk up a moving escalator. The man walks twice as fast as his wife. When he arrives at the top, he has taken 28 steps. When she arrives at the top, she has taken 21 steps. How many steps are visible in the escalator at any one time.
Answered by Peeny Nom and Claude Tardif. |
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What is 20 to the thousandth power? |
2002-02-12 |
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From Kristi:
What is 20 to the thousandth power?
Answered by Paul Betts. |
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Three bugs on a line |
2002-02-12 |
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From Murray:
- Three bugs are crawling on the coordinate plane. They move one at a time, and each bug will only crawl in a direction parallel to the line joining the other two.
- If the bugs start out at (0,0), (3,0), and (0,3), is it possible that after some time the first bug will end up back where it started, while the other two bugs switch places?
- Can the three bugs end up at (1,2), (2,5), and (-2,3)?
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- A single peg is placed at the bottom left-hand corner of a grid that extends infinitely far up and to the right. You play a game in which you are allowed to make the following move: if the hole immediately above and the hole immediately to the right of a peg are both empty, you can remove the existing peg and place pegs in those two holes instead.
- Show that, no matter how you move, you can never remove all the pegs from the 3-by-3 square at the bottom left-hand corner of the grid. (b)
- Is it possible to remove all the pegs from the six holes closest to the bottom left-hand corner of the grid (the region indicated in the picture below)?
Answered by Claude Tardif. |
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The slopes of the sides of the Great Pyramid |
2002-02-09 |
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From Christina:
The Great Pyramid is the largest of the Egyptian pryamids. When it was built, it was 481 feet tall and had a square base with 755-foot sides. The pyramid has two different slopes-one along its sides and the other along its edges. Which slope is steeper?
Answered by Penny Nom. |
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The number of hidden cubes |
2002-02-05 |
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From Katie:
This problem is about finding the number of cubes visible and hidden in a cube.
In a cube that is 3x3, 19 cubes can be seen. 8 are hidden.
In a cube that is 4x4, 37 cubes can be seen. 27 are hidden.
In a cube that is 5x5, 61 cubes can be seen. 64 are hidden.
In a cube that is 6x6, 91 cubes can be seen. 125 are hidden. The question is:
Explain how you could find the number of small cubes that are visible and hidden in a cube of any size.
Answered by Paul Betts and Penny Nom. |
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Parabolas |
2002-02-03 |
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From Kuang:
-Who is credited for working with or studying the Parabola? -What is a conic section? -What does a parabola look like? -How is a parabola formed? -Where and how are parabolas used today in the real world?
Answered by Harley Weston. |
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Number conversions and averages |
2002-02-03 |
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From A student:
A table has the measurements of 1.6m by 2m, how much material is needed to cover table? I converted to cm then multiplied but got an answer of 32000cm ,so I divide by 100 to get to metres - the answer was 320 which I know is wrong - please explain!! Also I need to explain in my own words what an 'average' is and I am struggling.
Answered by Penny Nom. |
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Square arrangements of clovers |
2002-02-03 |
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From Cassie:
Clyde had a strange fascination with numbers. One day he decided to mount his 4 leaf clover collection in groups of square numbers.he took a long piece of butcher paper and glue and began this arduous task.There was 1 clover,4 clovers.and then 9 clovers in the third set. what would be in the seventh set of 4 leaf clovers?
Answered by Penny Nom. |
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Zeta[2]=(Pi2)/6 |
2002-02-02 |
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From alex:
Can you please tell me a proof that Zeta[2]=(Pi2)/6
Answered by Chris Fisher. |
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I am a fraction |
2002-02-01 |
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From Anthony:
I am a fraction that is greater than 1 but less than 2. The sum of my numerator and denominator is 11. My denominator subtracted from my numerator is 1. What fraction am I?
Answered by Paul Betts. |
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