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 Math Central Quandaries & Queries
 Question from Mr, a teacher: The cold tap can fill a bath in 5minutes,the hot tap in 15,and the waste pipe empty the full bath in 10 minutes. All three are fully open for 2 minutes,after which the waste-pipe is closed. How much longer will it take to fill the bath?

Hi,

The cold tap fills the bath at the rate of one fifth of a tub per minute. The hot water tap fills the tub at the rate of one fifteenth of a tub per minute. Thus if they are both on they are filling the tub at

$\frac15 + \frac{1}{15} \mbox{ of a tub per minute.}$

At what rate does the waste pipe fill the tub? If all three are fully open at what rate is the tub being filled? At this rate how much of the tub is filled in 2 minutes?

Can you complete the problem now?

Write back if you need more assistance,
Penny

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