Two pipes A and B can fill a tank in 20 minutes and 30 minutes respectively. Both are opened together, but pipe A is closed after 5 minutes. How much more time will pipe B alone take to fill the rest of the tank?

Question

Accepted Answer

17.5. Combined rate = 1/12 per minute; in 5 minutes 5/12 is filled, leaving 7/12; B fills it in (7/12) ÷ (1/30) = 17.5 minutes.

Two pipes A and B can fill a tank in 20 minutes and 30 minutes respectively. Both are opened together, but pipe A is closed after 5 minutes. How much more time will pipe B alone take to fill the rest of the tank?

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