Q166
ArithmeticTime & Work, Pipes & Cisterns
Pipe A can fill a tank in 15 minutes and pipe B can drain 40 litres per minute. If both the pipes are opened together, the cistern is full in 45 minutes, find the capacity of the cistern.
- a.600 litres
- b.750 liters
- c.900 liters
- d.1800 liters
Answer: (C) 900 liters
For capacity C, A fills $\frac{C}{15}$ litres a minute and together they fill $\frac{C}{45}$ a minute. So $\frac{C}{15} - 40 = \frac{C}{45}$, giving $\frac{2C}{45} = 40$ and C = 900 litres. Check: A gives 60 litres a minute, net 20, and 900 ÷ 20 = 45 minutes.