SOLUTION: An inlet pipe on a swimming pool can be used to fill the pool in 20 hours. The drain pipe can be used to empty the pool in 21 hours. If the pool is 1/3 filled and then the inlet pi

Question 1000750: An inlet pipe on a swimming pool can be used to fill the pool in 20 hours. The drain pipe can be used to empty the pool in 21 hours. If the pool is 1/3 filled and then the inlet pipe and drain pipe are opened, how long from that time will it take to fill the pool?
Answer by addingup(3677) (Show Source): You can put this solution on YOUR website!
In 1 hour the pool fills 1/20
In 1 hour the pool empties 1/21
1/20-1/21= 1/3T Multiply all sides by 420 (20*21, it's the common denominator)
21-20= 140/T
1= 140/T Invert both terms:
1/1= T/140 Multiply both sides times 140:
140= T You need 140 hours
RELATED QUESTIONS
An inlet pipe on a swimming pool can be used to fill the pool in 18 hours. The drain pipe (answered by josgarithmetic)

An inlet pipe on a swimming pool can be used to fill the pool in 20 hours. The drain pipe (answered by josgarithmetic)

An inlet pipe on a swimming pool can fill the pool in 15 hours. The drain pipe can be... (answered by richwmiller)

An inlet pipe on a swimming pool can be used to fill a pool in 36 hours. The drain pipe... (answered by josgarithmetic)

an inlet pipe on a swimming pool can be used to fill a pool in 32 hours. The drain pipe... (answered by solver91311,lwsshak3)

An inlet pipe on a swimming pool can be used to fill the pool in 23 hours. The drain pipe (answered by mananth)

An inlet pipe on a swimming pool can be used to fill the pool in 32 hours. The drain pipe (answered by josgarithmetic)

an inlet pipe on a swimming pool can be used to fill the pool in 10 hours. The drain pipe (answered by mananth)

An inlet pipe on a swimming pool can be used to fill the pool in 25 hours. the drain pipe (answered by stanbon)