Question

An inlet pipe on a swimming pool can be used to fill the pool in 15 hours. The drain pipe can be used to empty the pool in 20 hours. If the pool is
`(1)/(3)` filled and then the inlet pipe and drain pipe are opened, how many more hours would it take to fill the pool? Round your answer to two decimal places, if needed.

_____________ hours

Answer 1

• 40 hours

Explanation:

• Rate of filling is 1/15
• Rate of draining is 1/20

If both lines are open the rate of filling is:

• 1/15 - 1/20 = 4/60 - 3/60 = 1/60 per hour

Since tank is 1/3 full we need to fill the remaining 2/3 of it.

Time required:

• 2/3 : 1/60 =
• 2/3*60 =
• 40 hours