A water tank has an inlet pipe and a drain pipe. A full tank can be emptied in 30 minutes if the drain is opened and an empty tank can be filled in 45 minutes with the inlet pipe opened. If both pipes are accidetally opened when the tank is full, then how long will it take to empty the tank?
2007-02-24 09:33:17 · 4 answers · asked by Help please 1 in Science & Mathematics ➔ Mathematics
In 1 minute,the outlet pipe can empty 1/30 th part of the tank
in 1 minute,the inlet pump can fill 1/45 th part of the tank
Hence if both the pipes are opened,the part of the tank that can be emptie in 1 minute is
1/30-1/45
=1/90 part
Hence,if the tank is full and noth the pipes are opened,the tank will be emptied in 1/1/90 or 90 minutes.
2007-02-24 09:43:40 · answer #1 · answered by alpha 7 · 2⤊ 0⤋
This is a work problem.
x = time in minutes
x/30 - x/45 = 1
3x - 2x = 90
x = 90 minutes
It will take 90 minutes to empty the tank.
2007-02-24 09:49:16 · answer #2 · answered by Northstar 7 · 1⤊ 0⤋
let t be the time, t/30 is the amount of emptying per minute, t/45 is the amount of filling per minute (as fractions of 1 entire tank full), so
1 - t/30 + t/45 = 0
90 - 3t + 2t = 0
t = 90 min.
2007-02-24 09:46:48 · answer #3 · answered by Philo 7 · 1⤊ 0⤋
75 minutes, I think...
2007-02-24 09:40:21 · answer #4 · answered by nintendo_obsession 2 · 0⤊ 1⤋