What is the correct answer?


Two pipes A and B can fill a tank in 36 bours and 46 bours respectively. If both the pipes are opened simultaneously, bow mucb time will be taken to fill the tank?

A. 18 hrs

B. 13 hrs

C. 20 hrs

D. 23 hrs

Correct Answer :

C. 20 hrs

       Part filled by A in 1 hour = (1/36);

       Part filled by B in 1 hour = (1/45);

        Part filled by (A + B) In 1 hour =(1/36)+(1/45)=(9/180)=(1/20)

       Hence, both the pipes together will fill the tank in 20 hours.