Number of 360-degree rotations that a bicycle wheel made

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S6-6 What is the number of 360-degree rotations that a bicycle wheel made while rolling 100 meters in a straight line without slipping?

(1) The diameter of the bicycle wheel, including the tire, was 0.5 meter.
(2) The wheel made twenty 360-degree rotations per minute.

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mehravikas wrote:S6-6 What is the number of 360-degree rotations that a bicycle wheel made while rolling 100 meters in a straight line without slipping?

(1) The diameter of the bicycle wheel, including the tire, was 0.5 meter.
(2) The wheel made twenty 360-degree rotations per minute.
The number of rotations = total distance/distance traveled in 1 rotation

We know the total distance, so we need to know the distance traveled in one rotation. For a circle, that's merely the circumference.

(1) Gives us diameter, so we can calculate circumference: sufficient.

(2) Gives us rate, which has nothing to do with the size of the circle: insufficient.

(1) is suff, (2) isn't: choose (A).
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by GMAT680 » Sat Mar 13, 2010 6:01 am
Doesn't statement 2 mean it needs 20 revolution to complete the 100 meters. Hence, 2*PI*r*20 = 100 and solve for r.

I thought this is enough information to solve the problem.

My answer is D and I am still not convinced. Can someone tell me why I am wrong?

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by kstv » Sat Mar 13, 2010 8:01 am
What is the number of 360-degree rotations that a bicycle wheel made while rolling 100 meters in a straight line without slipping?
(1) The diameter of the bicycle wheel, including the tire, was 0.5 meter.
(2) The wheel made twenty 360-degree rotations per minute.
You are assuming that it covered 100 mts in 20 revolutions.
Doesn't statement 2 mean it needs 20 revolution to complete the 100 meters. Hence, 2*PI*r*20 = 100 and solve for r.
Why even bother to calculate the part - 2*PI*r*20 = 100 and find r - you have to find the no of revolutions . Qs is
What is the number of 360-degree rotations that a bicycle wheel made while rolling 100 meters. According to you it is 20.

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mehravikas wrote:
Tue Jun 03, 2008 1:48 pm
S6-6 What is the number of 360-degree rotations that a bicycle wheel made while rolling 100 meters in a straight line without slipping?

(1) The diameter of the bicycle wheel, including the tire, was 0.5 meter.
(2) The wheel made twenty 360-degree rotations per minute.
Solution:

We need to determine the number of 360-degree rotations that a bicycle wheel made while rolling 100 meters in a straight line without slipping. If we can determine the circumference of the wheel, then we can determine the number of 360-degree rotations. For example, if the circumference of the wheel is 5 meters, then the number of the 360-degree rotations is 100/5 = 20.

Statement One Alone:

Since we know the diameter of the wheel, we can determine the circumference of the wheel and hence the number of 360-degree rotations. Statement one alone is sufficient.

Statement Two Alone:

Knowing the wheel made twenty 360-degree rotations per minute does not allow us to determine the circumference of the wheel. Hence, we can’t determine the number of 360-degree rotations. Statement two alone is not sufficient.

Answer: A

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