Multiple choice

If A and B together can complete a work in 18 days, A and C together in 12 days and B and C together in 9 days, then B alone can do the work in

  1. 18 days

  2. 24 days

  3. 30 days

  4. 40 days
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Let the work be 1 unit. Combined rates: A+B = 1/18, A+C = 1/12, B+C = 1/9. Adding all three: 2(A+B+C) = 1/18 + 1/12 + 1/9 = 9/36 = 1/4, so A+B+C = 1/8. Then B = (A+B+C) - (A+C) = 1/8 - 1/12 = 1/24. Therefore B alone takes 24 days.

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