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One pipe fills a tank 10 hours faster than another. Together they fill it in 12 hours. How long does the slower pipe take alone?

Competition practicePipes & Cisterns

A22 h
B30 h
C20 h
D24 h

Step-by-Step Solution

Let the slower take

t

h:

\frac{1}{t} + \frac{1}{t - 10} = \frac{1}{12} \Rightarrow t^{2} - 34 t + 120 = 0 \Rightarrow t = 30 (t = 4

is impossible). The faster takes 20 h.

Answer: B) 30 h

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