Question

One tap fills a tank in 3 hours and the other in 4
hours. The outlet can empty the tank in 2 hours.
In what time will the tank be filled if both the
taps are turned on and the outlet has been left
open accidentally?​

Answer 1

Given:

Time taken by 1st tank to fill = 3 hours

Time taken by 2nd tank to fill = 4 hours

Time taken by the outlet to empty the tanks = 2 hours

To find:

In what time will the tanks be filled.

Solution:

For the 1st tank:

Part of tanks filled in one hour = 1/3rd + 1/4th

Part of tanks emptied in one hour = 1/2

Part of the tank filled in one hour = 1/3 + 1/4 - 1/2 = 1/12

Therefore the tank will be filled in 12 hours.

The time taken by the tanks to be completely filled will be 12 hours.