Pipes A and B, when working together, can fill an empty tank in 8 hours. If B is stopped after 2 hours, it will take a total of 11 hoursto fill the tank. How long would it take A to fill the empty tank alone?

A can fill the empty tank alone in ( 12/1 × 1 ) = 12 hours.

Step-by-step explanation:

let, ( A + B ) means A and B work together.

( A + B) can fill an empty tank in 8 hours and after 2 hours B was stopped. That means first 2 hours A and B worked together.

( A + B) can fill a 2/8 = 1/4 part in 2 hours.

after 2 two hours, A fill the remaining part of tank which is ( 1 - 1/4 ) = 3/4 in    ( 11- 2) = 9 hours

It means A can fill ( 3/4 × 1/9 ) = 1/12 part in 1 hour.

Therefore, A can fill the empty tank alone in ( 12/1 × 1 ) = 12 hours.