Multiple choice

$25$ students can do a job in $12$ days, but on the starting day, five of them informed thet they are not coming. By what fraction will the number of days required for doing the whole work get increased?

  1. $\dfrac35$
  2. $\dfrac37$
  3. $\dfrac34$
  4. $\dfrac14$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Initial work = 25 * 12 = 300 man-days. With 20 workers, days required = 300 / 20 = 15 days. The increase in days is 15 - 12 = 3 days. The fraction of increase is 3/12 = 1/4.

AI explanation

Using the constant product of men and days, the total work is 25 students times 12 days, which equals 300 student-days. With 5 students absent, the new workforce is 20 students, so the work is completed in 300 divided by 20 days, giving 15 days. The original time was 12 days, so the increase is 3 days. The required fraction is 3 divided by 12, which simplifies to 1/4.

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