Question

pipe a can completely fill a tank in 6 hours whereas another pipe b can empty the tank in 7 hours if both pipes are opened together how long will it take to fill the tank completely​

Answer 1

Step-by-step explanation:

Pipe A can fill the tank in 6 hrs, So A's 1 hr Work = 1/6

Pipe B can empty a full tank in 7 hrs, So B's 1 hr Work  = -1/7

Now both the pipes are opened

(A+B)'s work = (1/6) + (-1/7)

                     = 1/ 42

So Both the pipe will take 42 hours to fill up the tank completely