Question

Two Pipes X and Y can fill a cistern in 10 hrs and 15 hrs respectively. If two pipes are working simultaneously then how much time will the tank be filled? 
1. 12 hr
2. 10 hr
3. 6 hr
4. 14 hr
5. None of these

Answer 1

Correct Answer - Option 3 : 6 hr

Given:

Pipe X can fill the tank in 10 hr

Pipe Y can fill the tank in 15 hr

Concept used:

Pipe A can fill a tank = x hr

⇒ Pipe A can fill a tank in 1 hr = 1/x

Calculation:

Pipe X can fill the tank in 1 hr = 1/10

Pipe Y can fill the tank in 1 hr = 1/15

⇒ Pipe (X + Y) can fill the tank in 1 hr = (1/10) + (1/15) = 5/30 = 1/6

∴ Pipe (X + Y) can fill the tank in 6 hr.