Multiple choice

A man, a woman and a boy can complete a work in 20 days, 30 days and 60 days respectively. How many boys must assist 2 men and 8 women so as to complete the work in 2 days?

  1. 4

  2. 6

  3. 8

  4. 12
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

A man's 1-day work is 1/20, a woman's is 1/30, and a boy's is 1/60. In 2 days, 2 men complete 2*(2/20) = 1/5 of the work, and 8 women complete 2*(8/30) = 8/15. Let x boys assist; they complete 2*(x/60) = x/30 of the work. Total: 1/5 + 8/15 + x/30 = (22+x)/30 = 1, so x = 8. Eight boys are needed.

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