Two horses begin running on an oval course at the same time. One runs each lap in 9 minutes; the other takes 12 minutes to run each lap. How Many minutes after the start will the faster horse have a one lap lead?	Options:
A) 36	B) 12	C) 9	D) 4	E) 3
The rate of the faster horse is 1/9 lap/minute;   The rate of the slower horse is 1/12 lap/minute;   Their relative rate is 1/9-1/12=1/36 lap/minute;   The faster horse to gain one full lap will need time=distance/rate=1/(1/36)= 
<gadget id="calculator">1/(1/36)</gadget>
<output>36</output>
36 minutes.   36nswer: 36.
<result>A</result>
Two horses begin running on an oval course at the same time. One runs each lap in 9 minutes; the other takes 12 minutes to run each lap. How Many minutes after the start will the faster horse have a one lap lead?