A pipe fills a tank in $10$ hr and a leak empties it in $15$ hr. With both open, the tank fills in:

A pipe fills a tank in $10$ hr and a leak empties it in $15$ hr. With both open, the tank fills in:
  1. $25$ hr
  2. $30$ hr
  3. $35$ hr
  4. $5$ hr

Solution

Net rate $= \dfrac{1}{10} - \dfrac{1}{15} = \dfrac{3 - 2}{30} = \dfrac{1}{30}$/hr. Time $= 30$ hr.

Asked in: IMO

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