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Pipe A fills a tank 8 minutes faster than pipe B. Together they fill it in 3 minutes. How long does B alone take?

Competition practicePipes & Cisterns

A4 min
B6 min
C8 min
D12 min

Step-by-Step Solution

Let A take

x

min,

B

take

x + 8. \frac{1}{x} + \frac{1}{x + 8} = \frac{1}{3} \Rightarrow x^{2} + 2 x - 24 = 0 \Rightarrow x = 4. B = 12

min. Check:

\frac{1}{4} + \frac{1}{12} = \frac{1}{3}

✓.

Answer: D) 12 min

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