Pipe A and B fill a tank in 20 hours and 7 hours respectively. If after starting working together pipe A is stopped after 2 hours then in how much time B take to fill the remaining tank?

\(\frac{86}{20}\)

Efficiency of A + B = 7 + 20 = 27

After two hours remaining work = 140 - (27) × 2

                                                   = 140 - 54 = 86

Now B will do remaining work in = \(\frac{86}{20}\) hrs