Multiple choice

20 labourers, working 7 hours a day can finish a piece of work in 30 days. If the labourers work 5 hours a day, then the number of labourers to finish the same piece of work in 40 days, will be :

  1. 15

  2. 21

  3. 22

  4. 25
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Use the formula (M1 * D1 * H1) / W1 = (M2 * D2 * H2) / W2. Here, (20 * 30 * 7) / 1 = (M2 * 40 * 5) / 1. So 4200 = 200 * M2, which means M2 = 21.

AI explanation

Using the formula for man-days, we equate the total hours of work required for the job: (20 labourers) multiplied by (30 days) multiplied by (7 hours) equals (number of labourers) multiplied by (40 days) multiplied by (5 hours). This gives 4200 equal to 200 times the number of labourers. Solving this equation gives 21 labourers needed to finish the work in 40 days.

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