A bath tub can be filled with the cold water pipe in 10 minutes and by hot water pipe in 15 minutes (independently each). A person leaves the bathroom after turning on both pipes simultaneously and returns at the moment when the bath should be full. Finding, however, that the waste pipe has been opened he now closes it. In 4 minutes more, the bath is full. In what time would be the waste pipe empty it?

A bath tub can be filled with the cold water pipe in 10 minutes and b

1.	A bath tub can be filled with the cold water pipe in 10 minutes and by hot water pipe in 15 minutes (independently each). A person leaves the bathroom after turning on both pipes simultaneously and returns at the moment when the bath should be full. Finding, however, that the waste pipe has been opened he now closes it. In 4 minutes more, the bath is full. In what time would be the waste pipe empty it?
Answer» 6 minutes 9 minutes 3 minutes 15 minutes Solution :LET 180 units be the CAPACITY of tub P and Q together can fill tank in `180/(18+12)=6 `min `therefore` we can say, Work done by 'R' in 6 min = work dons by (P&Q) Together in 4 minutes `rArr 6 cdot x = 4 xx (18+12)` `rArr x= 20` `therefore` R is doing 20 units of work in 1 minute `therefore` requires `180/20=9` minutes to empty tank