A tap can empty a tank in one hour. A second tap can empty it in 30 minutes. If both the taps operate simultaneously, how much time is needed to empty the tank?
Q. A tap can empty a tank in one hour. A second tap can empty it in 30 minutes. If both the taps operate simultaneously, how much time is needed to empty the tank?
Answer: 20 minutes
Notes: 1 hour = 60 minutes Rate of emptying the tank by the two taps are $latex \frac{1}{60}&s=1$ and $latex \frac{1}{30}&s=1$ of the tank per minute respectively. Rate of emptying the tank when both operate simultaneously = $latex = \frac{1}{60} + \frac{1}{30} = \frac{1+2}{60} = \frac{3}{60} = \frac{1}{20}&s=1$ of the tank per minute. ∴ Time taken by the two taps together to empty the tank = 20 minutes. Hence option [B] is the right answer.