Question

A 12-gallon tub has a faucet that lets water in at a rate of 3 gallons per minute, and a drain that lets water out at a rate of 1.5 gallons per minute. If you start with 3 gallons of water in the tub, how long will it take to fill the tub completely?

Answer 1

Vol of water required to fill up the tub = 12-3 = 9
Rate of water per min = 3 -1.5 = 1.5/min
Using the formula vol = rt
t = v/r
t = 9/1.5 = 6
time taken = 6 mins