One pipe fills a tank 12 hours faster than another. Together they fill it in 8 hours. How long does the faster pipe take alone?
Correct answer D. 12 hours
Explanation
If the faster takes x hours, x(x + 12)/(2x + 12) = 8, giving x² − 4x − 96 = 0. So x = 12 hours (the slower takes 24).
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