Multiple choice

X, Y and Z together can complete a job in 10 days. The rate of work of X is three times that of Y, which, in turn is twice that of Z. What is the time taken by Z alone to complete the job?

  1. 30 days

  2. 60 days

  3. 90 days

  4. 120 days

  5. 180 days
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Let Z's rate be z. Y's rate = 2z. X's rate = 3 * 2z = 6z. Total rate = 6z + 2z + z = 9z. Total work = 10 days * 9z = 90z. Time for Z = 90z / z = 90 days.

AI explanation

The work rates form a ratio where X is six times Z and Y is twice Z. Let Z's rate be 1 unit per day, making Y's 2 and X's 6, for a combined rate of 9 units per day. Since they complete the job in 10 days, the total work is 90 units. Z alone takes 90 units divided by 1 unit per day to finish the job. The answer is 90 days.

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