Question

Two taps a and b can fill a tank in 45 minutes and 36 minutes if both taps are opened

Answer 1

a's 1min work = 1/45

b's1min work = 1/36

(a + b )'s work =1/45 +1/36

= 4 + 5/180

= 9/180 = 1/20

so tap a and b together fill tank in 20 minutes