Question

two pipes A and B can separately fill a cistern in 4 hours and 6 hours respectively while a third pipe C can empty the full cistern in 8 hours. If all the pipes are opened together in what time the empty cistern is filled ?​

Answer 1

Answer: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.  

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