Question

A water tank that holds 60 gallons is filled at a rate of 4/5 of a gallon per second. How long does it take to fill the tank to 2/3 of its capacity?

Answer 1

2/3 of its capacity - 60 * 2/3 gallons = 40 gallons.

Time to fill to 2/3 is 40 / 4/5 = 40 * 5 / 4

= 50 seconds (answer)