Question: Tom's rabbit can run at 25 miles per hour.  His cat can run 20 miles per hour.  The cat gets a 15-minute head start.  In hours, how long will it take for the rabbit to catch up?
Solution:
The cat got a 15/60=.25 hour head start
That means it ran 20*.25=5 miles
The rabbit goes 25-20=5 mph faster than the cat
So it takes 5/5=1 hour for the rabbit to catch up
Answer: 1