two pools are leaking. after 15 minutes (1/4 hour), pool A has leaked 2/3 of a gallon. after 20 minutes (1/3 hour) pool B has leaked 3/4 of a gallon. which pool is leaking faster
If you were to look at a full hour of loss you would count that the first pool loses 2 2/3 gallons per hour while the second pool only loses 2 1/4 gallons per hour.