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Question
12 pipes, all of the same size, fill a tank in 42 minutes. How long will it take to fill the same tank, if 21 pipes of the same size are used?
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Solution
Pipes: Time:: Pipes: Time
12 : 2x :: 21 : 42
∴ By inverse proportion
12 × 42 = 21 × x
`⇒"x"=(12xx42)/21`
= 24 minutes
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