A workforce of $420$ men with a contractor can finish a certain piece of work in $9$ months. How many extra men mist be employ to complete the job in $7$ months?

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Solution

Men Time
$420$ $9$ months
$x$ $7$ months
As the number of workers is inversely proportional to time taken:
$420 \times 9 = x \times 7 ⟹ x = \frac{420 \times 9}{7} = 540$
$∴$ extra men needed: $540 - 420 = 120$

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A workforce of 420 men with a contractor can finish a certain piece of work in 9 months. How many extra men mist be employ to complete the job in 7 months?

Men Time420 9 monthsx 7 monthsAs the number of workers is inversely proportional to time taken:420×9=x×7⟹x=420×97=540∴ extra men needed: 540−420=120

A workforce of $420$ men with a contractor can finish a certain piece of work in $9$ months. How many extra men mist be employ to complete the job in $7$ months?

Men Time
$420$ $9$ months
$x$ $7$ months
As the number of workers is inversely proportional to time taken:
$420 \times 9 = x \times 7 ⟹ x = \frac{420 \times 9}{7} = 540$
$∴$ extra men needed: $540 - 420 = 120$