Question

15 men can do a piece of work in 36 hours .. How many men required to finish the work in 20 hours

Answer 1

Known that the no. of workers and the time taken to finish the work are inversely proportional.

Thus, as no. of workers is increased by 'k' times, the time reduces to its '1/k' part.

E.g.: On increasing no. of workers 2 times, the time reduces to its half.

Given that 15 men can do a piece of work in 36 hours.

⇒ No. of men required to complete the piece of work in ''36'' hours = ''15''

⇒ No. of men required to complete the piece of work in ''36/36 = 1'' hour = ''15 × 36 = 540''

⇒ No. of men required to complete the piece of work in ''1 × 20'' hours = ''540/20 = 27''

Thus 27 men will be required to finish the piece of work in 20 days.

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Answer 2

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8. men.

$15 = 36 \: hrs \\ ? = 20 \: hrs \\ \frac{15}{36} = 0.4166 = 0.42 \\ ie \: 20 \times 0.42 = 8 \\ so \: 8 \: men \: required \: to \: finish \: work \: in \: 20 \: hours.$