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The tank shown has three pipes. One morning only two of them were open, and the empty tank took exactly 30 hours to fill. Which pipe was closed?

Class 8Pipes and CisternsDirect and Inverse Proportions

APipe A
BPipe B
CPipe C
DNo pipe was closed

Step-by-Step Solution

A and C:

\frac{1}{12} - \frac{1}{20} = \frac{5 - 3}{60} = \frac{1}{30}

→ 30 h. (A and B take

6 \frac{2}{3}

h, B and C take 60 h.) So B was closed.

Answer: B) Pipe B

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