A circular rim 14 inches in diameter rotates the same number of inches per second as a circular rim 21 inches in diameter. If the smaller rim makes x revolutions per second, how many revolutions per minute does the larger rim makes in terms of x ?	Choices:
A) 48pi/x	B) 40x	C) 48x	D) 24x	E) x/75
Let's try the explanation. We have two wheels. One with 14pi and the other one with 21pi. They have the same speed. In the smaller wheel it's 14pi*x, which must be equal to the speed of the bigger one (21pi*a number of revolutions).They are asking that number of revolutions (but in minutes, which makes the question even harder).   Anyway, we have 14pi*x=21pi*a.   (14pi*x)/(21pi). As I said, that's in seconds. So, to convert it to minutes we multiply by 60 and we get the result, 40x.   Ans : 40x
<result>B</result>
A circular rim 14 inches in diameter rotates the same number of inches per second as a circular rim 21 inches in diameter. If the smaller rim makes x revolutions per second, how many revolutions per minute does the larger rim makes in terms of x ?