63 men can complete a piece of work in 30 days. In how days can 21 men complete the same piece of work?

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CSIR-CLRI JSA 2024 Official Paper-I (Held On: 16 Feb, 2025)
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  1. 70
  2. 90
  3. 85
  4. 88

Answer (Detailed Solution Below)

Option 2 : 90
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Detailed Solution

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Given:

63 men can complete a piece of work in 30 days.

Formula used:

Work = Number of men × Number of days

Calculation:

Work done by 63 men in 30 days = 63 × 30

⇒ Work = 1890 man-days

Let the number of days required for 21 men to complete the same work be x.

⇒ Work done by 21 men in x days = 21 × x

Since the work is the same, we can set up the equation:

21 × x = 1890

⇒ x = 1890 / 21

⇒ x = 90

∴ The correct answer is option (2).

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