Question

An inlet pipe on a swimming pool can be used to fill the pool in 30 hours. The drain pipe can be used to empty the pool in 34 hours. If the pool is 15 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.

Answer 1

• 204 hours

Explanation:

The filling speed is 30 hours or:

• 1/30 in an hour

The draining speed is 34 hours or:

• 1/34 in an hour

If both lines are open simultaneously, the filling speed is:

• 1/30 - 1/34 =
• 17/510 - 15/ 510 =
• 2/510 =
• 1/255 in an hour

If the tank is 1/5 full, then we need to fill the 4/5 of level and it will take:

• 4/5 : 1/255 =
• 4/5 *255 =
• 204 hours