Multiple choice

Eight boys and 12 girls can complete a piece of work in 8 days, and 14 girls with 6 boys can do the same work in 10 days. Find the time taken by 20 girls to complete the work.

  1. 12 days

  2. 40 days

  3. 6 days

  4. 9 days

  5. 16 days
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Let B be the work of a boy per day and G be the work of a girl per day. 8B + 12G = 1/8 and 6B + 14G = 1/10. Solving this system: multiply first by 3 and second by 4: 24B + 36G = 3/8 and 24B + 56G = 4/10. Subtracting gives 20G = 4/10 - 3/8 = 16/40 - 15/40 = 1/40. Thus, 20 girls complete the work in 40 days.

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