Pipe A can fill the tank 2 times faster than pipe B. If pipe A and B together…

Concept

When two pipes fill the same tank, their filling rates (tank per minute) ADD. If a pipe alone takes T minutes, its rate is 1/T tank per minute. "Two times faster" means the rate is doubled (so the time is halved).

Application

1. Let Pipe B's rate be x tank per minute, so the slower pipe is B.

2. Pipe A is twice as fast, so Pipe A's rate = 2x tank per minute.

3. Working together their combined rate fills the tank in 24 minutes, so x + 2x = 1/24.

4. 3x = 1/24 → x = 1/72 tank per minute.

5. Time for Pipe B alone = 1 ÷ x = 72 minutes.

Cross-check

If B takes 72 minutes then A takes 36 minutes. Combined rate = 1/72 + 1/36 = 1/72 + 2/72 = 3/72 = 1/24, which fills the tank in 24 minutes as required.