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Pipe A fills a tank in 6 hours and pipe B in 9 hours. Which statement is true?

Competition practicePipes & Cisterns

ATogether they need 3.6 h
BTogether they need 7.5 h
CTogether they fill $\frac{1}{15}$ per hour
DA fills $\frac{1}{9}$ per hour

Step-by-Step Solution

\frac{1}{6} + \frac{1}{9} = \frac{5}{18}

per hour →

\frac{18}{5} = 3.6

h ✓. 7.5 h is the average of times;

\frac{1}{15}

adds the times; A fills

\frac{1}{6}

per hour.

Answer: A) Together they need 3.6 h

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