Multiple choice

It takes $8, 12$ and $16$ days for $X, Y$ and $Z$ respectively to complete a work. If $X$ works on it for $2$ days and then $Y$ works on it for until $25\%$ of the work is left for $Z$ to do, how many days it takes to complete the work?

  1. $10$ days
  2. $12$ days
  3. $8$ days
  4. $14$ days
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

X does 1/8 per day, Y does 1/12, Z does 1/16. X works 2 days (2/8 = 1/4 work). Remaining is 3/4. Y works until 25% (1/4) is left for Z. So Y does 1/2 of the work. Y's time = (1/2) / (1/12) = 6 days. Z does 1/4 work in (1/4) / (1/16) = 4 days. Total time = 2 + 6 + 4 = 12 days.

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