Pipe A fills a tank in 6 hours. Pipe B alone fills it in 9 hours. With both pipes open and a drain that empties the tank in 18 hours, how long does it take to fill the tank?

\frac{9}{2} hours Net rate = \frac{1}{6} + \frac{1}{9} - \frac{1}{18} = \frac{3 + 2 - 1}{18} = \frac{4}{18} = \frac{2}{9}. Time = \frac{9}{2} hours.

Linear Equations in One Variable

SAT Math· difficulty 5/5

6

Explanation

= \frac{1}{6} + \frac{1}{9} - \frac{1}{18} = \frac{3 + 2 - 1}{18} = \frac{4}{18} = \frac{2}{9}

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