Multiple choice

A takes 15 days to complete a piece of work and B takes 25 days to complete the same work. Both of them work together for 5 days and then, A leaves and B does the remaining work. What percent of total work is done by B?

  1. 33.33%

  2. 50%

  3. 55.25%

  4. 66.67%

  5. 75%
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

A's rate = 1/15, B's rate = 1/25. Together = (5+3)/75 = 8/75. In 5 days, work done = 5 * 8/75 = 8/15. Remaining work = 7/15. B does this alone. Total work by B = (5 * 1/25) + 7/15 = 1/5 + 7/15 = 3/15 + 7/15 = 10/15 = 2/3 = 66.67%.

AI explanation

Using the Least Common Multiple method, let the total work be 75 units. A completes 5 units per day and B completes 3 units per day. Working together for 5 days, they finish 8 * 5 = 40 units, leaving 35 units for B to complete alone. B's total contribution is the 15 units from the joint phase plus the 35 remaining units, totaling 50 units. Dividing B's 50 completed units by the 75 total units gives 66.67 percent.

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