Multiple choice

X, Y, and Z are three software experts, who work on upgrading the software in a number of identical systems. X takes an off after every 3 days of work, Y takes an off after every 4 days of work and Z takes an off after every 5 days of work. Starting afresh after a common day off: (i) X and Y working together can complete one new upgrade job in 6 days (ii) Z and X working together can complete two new upgrade jobs in 8 days (iii) Y and Z working together can complete three new upgrade jobs in 12 days If X, Y and Z together start afresh on a new upgrade job (after a common day off), exactly how many days will be required to complete this job?

  1. 2 days

  2. 3.5 days

  3. 2.5 days

  4. 4 days

  5. 3 days
Reveal answer Fill a bubble to check yourself
C Correct answer
AI explanation

The net combined work of X and Y is 1/6 job per day, X and Z is 2/8 job per day, and Y and Z is 3/12 job per day. Adding these three equations gives 2 times the net work of X, Y, and Z as 1/6 + 1/4 + 1/4 = 2/3 job per day. Therefore, the combined net work of all three is 1/3 job per day. To complete 1 job at this rate, they require exactly 3 days.

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