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The standard normal distribution |
2007-12-29 |
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From GEORGE:
Statistics texts state that in a normal distribution, 1 standard deviation covers 68%, 2SD 95% 3SD 99.7%. However, on looking at the tables for normal curve areas, the percentage for a z value of 1 is 84.13. 68 % of values are covered at a z value of 0.47. The discrepancies exist even for other values but are smaller. So why is the rule of thumb so different from the Table for Normal Curve areas?
Answered by Harley Weston. |
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Combinations of 1, 2, 3 |
2007-12-29 |
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From gary:
I can only write the numbers 1, 2, 3, in six different combinations. Are there any more possibilities
Answered by Penny Nom. |
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How would one find the radius? |
2007-12-29 |
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From Ned:
Given an arc with length of 192 inches (don't know chord length),
and arc height of 6 inches, how would one find the radius?
Answered by Stephen La Rocque and Harley Weston. |
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The centroid of a polygon |
2007-12-29 |
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From David:
I am playing around with an idea. I've read previous answers to questions
(using surveyor calculation methods) related to finding the area of an irregular
shape parcel of land (or irregular polygon). Is there a formula or method for
calculating the centroid (mid-point) for this type of polygon. I've seen plenty
of methods for calculating the mid-point for a triangle or regular shape poloygon
but few for an irregular shape polygon such as a parcel of land. Thanks...
Answered by Harley Weston. |
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Sally, Charlie and Snoopy in a race |
2007-12-29 |
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From Marie:
Sally and Charlie are having a race. Charlie gets a 900 foot lead and runs 8
inches per second. Sally begins at the starting line and runs at a rate of 5 ft per
second. Charlie's dog is also in the race. Snoopy starts 1100 feet ahead of Sally and runs
toward the starting line at a rate of 1 foot per second.
When will Charlie and Snoopy past each other and how far will they be from the starting line?
Answered by Penny Nom. |
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Calculate the two possible lengths of the third side. |
2007-12-28 |
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From Lisa:
An isosceles triangle has an area of 25.6 sq cm.
The two equal sides are 8.4 cm long.
Calculate the two possible lengths of the third side.
Answered by Penny Nom. |
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How many complete revolutions does each wheel make? |
2007-12-28 |
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From varoon:
The wheels of a car are of diameter 80cm each. How many complete revolutions does each wheel make in 10 minutes when the car is travelling at a speed of 66kms per hour?
Answered by Penny Nom. |
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Differentiate |
2007-12-28 |
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From taiwo:
i am finding it difficult to use first principle to differentiate this question: y=xcos2x. can u help me.
Answered by Penny Nom. |
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Finding the equation of a line from its graph |
2007-12-25 |
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From ken:
I have a graph and it is asking me to find the slope of each line, and
then write its equation. the graph show a negative slope. Would
appreciate the answer if you could show me how to do this question.
Kind regards: Ken
Answered by Stephen La Rocque. |
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The case of the forgotten umbrella |
2007-12-25 |
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From rougi:
a lecturer goes to a bar because it looks like raning.he takes an umbrella with him. on the way to bar he forgets the umbrella in the bus with probability 0,1,in the bar with probability 0.3 and on his way home in the taxi with probability 0,6
a)what is probability that he forgets the umbrella on his tripe?
b)when he gets home he realizes that he has forgotten his umbrella,what is probability that he has forgotten it in the taxi?
Answered by Stephen La Rocque and Harley Weston. |
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An irregular octagon |
2007-12-23 |
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From Sheldon:
I am attempting to construct an irregular octagon picture frame out of bamboo. The bamboo is 1" in diameter and the opening should be 20" H X 16"W.
What measurements should be used?
Answered by Penny Nom. |
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Two cars drive in opposite directions |
2007-12-23 |
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From dale:
2 cars starting from the same point in opposite direction on a straight highway drove 6 miles then turn left and drove 8 miles. How far apart are the cars?
Answered by Penny Nom. |
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The dimensions of a rectangle |
2007-12-22 |
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From Justin:
I'm trying to find the width of a rectangle. I have its area and its height. The area is 32 inches square and the width is 4 feet (48 inches). Can someone help explain this to me?
Answered by Penny Nom. |
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How many triangles can be formed? |
2007-12-21 |
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From pankaj:
Q.There is 2 lines parallel to each other. If 1st has 5 points in it and 2nd 3 points in it,how many triangles can be formed?
Answered by Penny Nom. |
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The probability of the second win on the third test |
2007-12-21 |
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From pankaj:
Q.The probability of india winning a test match against india is 1/2. Assuming independence from match to match. what is the probability that india's second win occurs at 3rd test in a 5 match series?
Answered by Penny Nom. |
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