Word Problem

Question

An aquarium tank can hold
6000
liters of water. There are two pipes that can be used to fill the tank. The first pipe alone can fill the tank in
40
minutes. The second pipe can fill the tank in
60
minutes by itself. When both pipes are working together, how long does it take them to fill the tank?

Answer 1

Each minute, the first pipe fills 1/40 of the tank and the second pipe fills 1/60 of the tank.  If it takes x minutes for both pipes working together to fill the tank, then, each minute, 1/x of the tank gets filled.

 

So, 1/40 + 1/60 = 1/x

 

Multiply both sides by the LCD, 120x:

 

3x + 2x = 120

 

5x = 120

 

x = 24 minutes