Question

a tank has 2 taps. when running alone one tap can fill the tank in 20 minutes while the second tap can fill the tank in 60 minutes. how long does it take to fill the tank if both the taps are running together?

Answer 1

Take the reciprocal of the time taken individually and then add them.
(1/20 + 1/60) Then do the reciprocal of the answer you get(1/15) get the actual answer. That is 15 minutes.