A circular rim 28 inches in diameter rotates the same number of inches per second as a circular rim 42 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 ?
Pick:
A) 48pi/x B) 75x C) 40x D) 24x E) x/75
It's C.   Let's try the explanation. We have two wheels. One with 28pi and the other one with 42pi. They have the same speed. In the smaller wheel it's 28pi*x, which must be equal to the speed of the bigger one (42pi*a number of revolutions).They are asking that number of revolutions (but in minutes, which makes the question even harder).   Anyway, we have 28pi*x=42pi*a.   (28pi*x)/(42pi). 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>C</result>
A circular rim 28 inches in diameter rotates the same number of inches per second as a circular rim 42 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 ?