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Mathematical Puzzles Hard 3 min

A can complete a job in 12 days and B can complete it in 18 days. If they work together at constant rates, how long will they take?

Hint
Add their daily work rates.

Answer

7.2 days, or 7 days 4 hours 48 minutes.

Explanation

A completes 1/12 of the job per day and B completes 1/18. Together they complete 5/36 per day, so the time is 36/5 = 7.2 days.

Step-by-Step Solution

Combined rate = 1/12 + 1/18 = 5/36.
Time = 36/5 = 7.2 days.
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