Question

Circular gears P and Q start rotating at the same time at constant speeds. Gear P makes 10 revolutions per minute and Gear Q makes 40 revolutions per minute. How many seconds after the gears start rotating will gear Q have made exactly 6 more revolutions than gear P ?

A. 6
B. 8
C. 10
D. 12
E. 15

Answer 1

12 minutes

Option D

Explanation:

Given that circuar gears P and Q start rotating at the same time at constant speeds.

Gear P makes 10 revolutions per minute and Gear Q makes 40 revolutions per minute.

Both gears start at the same time.

No of rotations per minute are 10 and 40

Difference is 30 in one minute

For 6 difference we must have exactly 1/5 minutes

which equals 12 seconds.

In 1/5 minutes or 12 seconds gear P would have completed 2 revolutions while Gear Q would have completed 8 revolutions thus making difference as 6.