Time ratio for X:Y to complete task is 5:3. Y alone takes 15 hours. X and Y together?

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Accepted Answer

1. Time ratio X:Y = 5:3 means X takes $5k$ hours and Y takes $3k$ hours.

2. Given Y = 15, so $3k=15$ ⇒ $k=5$. Thus X = $5k=25$ hours.

3. Combined rate = $1/25+1/15=8/75$. Time together = $\frac{75}{8}=9.375$ hours.

FINAL_ANSWER: b

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