Pipes A and B, opened together on an empty tank, fill it in 18 minutes. Pipe A alone can fill the empty tank in 30 minutes. How long will pipe B alone take to fill the empty tank?
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → 45 minutes
The one-minute work of A and B together is the sum of their separate one-minute works, so B's share = joint work − A's work.
A and B together fill \(\frac{1}{18}\) of the tank in one minute
A alone fills \(\frac{1}{30}\) of the tank in one minute
B alone fills \(\displaystyle \frac{1}{18}-\frac{1}{30}=\frac{5-3}{90}=\frac{2}{90}=\frac{1}{45}\) of the tank in one minute
Pipe B alone fills the tank in 45 minutes.