Multiple choice

A can complete 40% of a job in 10 days, while B can complete 60% of the same job in 15 days. If they work on it together, how many days will they take to complete 80% of the job?

  1. 10

  2. 12

  3. 15

  4. 16
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

A completes 40% in 10 days, so 100% in 25 days (rate 1/25). B completes 60% in 15 days, so 100% in 25 days (rate 1/25). Together rate = 2/25. Time for 80% = (80/100) / (2/25) = 0.8 * 12.5 = 10 days.

AI explanation

A completes the whole job in 10 divided by 0.4, which equals 25 days, so A's daily work rate is 1/25. B completes the whole job in 15 divided by 0.6, which equals 25 days, so B's daily work rate is also 1/25. Working together, their combined rate is 2/25 of the job per day. To complete 80% of the job, they need 0.8 divided by (2/25), which equals 10 days. The result is 10 days.

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