Pipe A fills water 4 times as fast as pipe B. When the tank is empty and both pipes are opened together, the tank is full in 9 minutes. How long would pipe B alone take to fill the empty tank?
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → 45 minutes
If B fills 1 unit per minute, A fills 4 units per minute. The capacity is then the joint rate multiplied by the joint time.
Together: \(4+1=5\) units per minute
Capacity \(=5\times9=45\) units
B alone \(\displaystyle =\frac{45}{1}=45\) minutes