A large tanker can be filled by two pipes A and B in 60 and 40 minutes respectively. How many minutes will it take to fill the tanker from empty state if B is used for half the time and A and B fill it together for the other half?

One Answer on this Question

1. 30mins

   Let the total time taken to fill the tank be x minutes.

   Then, work done by B in half hour + work done by (A+B) in half hour =1.

   (
   40
   1
   ​
   ×
   2
   x
   ​
   )+(
   60
   1
   ​
   +
   40
   1
   ​
   )×
   2
   x
   ​
   =1

   ⇒
   80
   x
   ​
   +
   48
   x
   ​
   =1

   ⇒
   240
   3x+5x
   ​
   =1

   ⇒8x=240

   ⇒x=30 min

   Reply