Inlet Pipe A can fill a tank in 30 minutes, and outlet pipes B and C can empty the tank in 2 hours each. If all 3 pipes operate together, the tank will be filled in:
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → 1 hour
The net rate of filling per hour is the inlet rate minus the outlet rates. A fills the tank in 30 minutes = \(\frac{1}{2}\) hour, so A fills 2 tanks per hour; B and C each empty \(\frac{1}{2}\) tank per hour.
\( \displaystyle \text{Net rate} = 2 - \frac{1}{2} - \frac{1}{2} = 1 \text{ tank per hour} \)
So the tank is filled in 1 hour.