A tank is filled in 45 minutes by two pipes, A and B. Pipe B fills the tank twice as fast as A. How much time (in minutes) will pipe A alone take to fill the tank?
Show answer & explanation
Correct answer: A
Explanation
The correct answer is option 1 i.e. 135.
Let the time required for pipe A to fill the tank = x minutes
So, the time required for pipe B = x/2 minutes
Pipe A's rate = 1/x of the tank filled per minute
Pipe B's rate = 1/(x/2) = 2/x of the tank filled per minute
So, 1/x + 2/x = 1/45
⇒ 3/x = 1/45
⇒ x = 3 × 45 = 135
Therefore, pipe A alone will take 135 minutes to fill the tank.