Question

Two pipes a and b can fill a tank in15 minutes and 20 minutes respectively.Both the pipes are opened together butafter 4 minutes, pipe a is turned off.What is the total time required to fill thetank?

Answer 1

Answer:

Step-by-step explanation:

A can fill a tank in 15 minutes

so,A's 1 minute work=1/15 part

B can fill the tank in 20 minutes

so,B's 1 minute work=1/20 part

So in 1 minute A and B can fill=1/15+1/20 part

                                                   =4+3/60 part

                                                   =7/60 part

A and B's 4 minutes work=7/60*4=7/15 part

Time taken by them to fill the tank=1/7/15=2 whole 1/7 minutes