Pipe A can fill a swimming pool in 10 hours.Pipe B can fill the same pool in 8 hours. If pipe A and pibe B work together for the first 2 hours and then pipe B stops working, how long will it take pipe A to finish the job?

Answer 1

in 2 hours, they can fill

2(1/10 + 1/8) = 9/20 of the pool. So, at 1/10 pool/hr, A takes an additional

(11/20) / (1/10) = 11/2 hours