Two pipes A and B can fill a tank in 20 and 30 minutes respectively. If both the pipes are used together, then how long will it take to fill the tank?
Answer: A
Part filled by A in 1 min = | 1 | . |
20 |
Part filled by B in 1 min = | 1 | . |
30 |
Part filled by (A + B) in 1 min = | ![]() |
1 | + | 1 | ![]() |
= | 1 | . |
20 | 30 | 12 |
Both pipes can fill the tank in 12 minutes.