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 15 more revolutions than gear P?  Choose the correct choice from the following choices.
A) 12	B) 15	C) 20	D) 24	E) 30
Gear Q makes 30 more revolutions each 60 seconds.   The time to make 15 = 30/2 more revolutions is 60/2= 
<gadget id="calculator">60/2</gadget>
<output>30</output>
30 seconds.   The answer is 30.
<result>E</result>
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 15 more revolutions than gear P?