Three pipes A, B, and C can fill a tank together in 10 hours. After working at it together for 2 hours, B is closed and A and C can fill the remaining part in 12 hours. The time in which B alone can fill the tank is
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → 30 hours
In 2 hours, A, B and C together fill \( \frac{2}{10}=\frac{1}{5} \) of the tank, so \( \frac{4}{5} \) is left.
A and C fill this \( \frac{4}{5} \) in 12 hours, so together they fill \( \frac{4}{5}\div 12=\frac{1}{15} \) of the tank per hour.
B alone fills, per hour,
\( \displaystyle \frac{1}{10}-\frac{1}{15}=\frac{3-2}{30} \)
\( \displaystyle =\frac{1}{30} \)
So B alone fills the tank in 30 hours.