Question

Pipes A and B can fill a tank in 12 minutes and 15 minutes, respectively. The tank when full can be emptied by pipe C in x minutes. When all the three pipes are opened simultaneously, the tank is full in 10 minutes. The value of x is:
1. 24
2. 18
3. 15
4. 20

Answer 1

Correct Answer - Option 4 : 20

Given:

A can-do 1 unit work = 1/12 minutes                                   

B can do 1 unit work = 1/15 minutes 

C can do 1 unit work = - 1/x minutes

Together they can fill the tank = 1/10 minutes

Formula used:

Total work = Efficiency × days

Solutions:

⇒ 1/total days = 1/A + 1/B - 1/C

⇒ 1/10 = 1/12 + 1/15 - 1/x

⇒ 1/x = 1/12 + 1/15 - 1/10

⇒ 1/x = (5 + 4 - 6)/60

⇒ 1/x = 3/60

⇒ x = 20

∴  The value of x is 20.