Multiple choice

Ronit, Alan and Paul can do a piece of work in 20, 30 and 60 days, respectively. In how many days can Ronit do the work, if he is assisted by Alan and Paul on every third day?

  1. 12 days

  2. 15 days

  3. 16 days

  4. 18 days

  5. None of these
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Ronit's rate is 1/20, Alan's is 1/30, and Paul's is 1/60. In a 3-day cycle, Ronit works alone for 2 days (2/20) and with others on the 3rd day (1/20 + 1/30 + 1/60 = 6/60 = 1/10). Total work in 3 days is 2/20 + 1/10 = 1/10 + 1/10 = 1/5. Thus, 5 cycles of 3 days (15 days) complete the work.

AI explanation

Taking the total work as 60 units, Ronit does 3 units per day, Alan does 2 units, and Paul does 1 unit. In a three day cycle, Ronit works alone for two days to complete 6 units, and on the third day all three work together to complete 6 units, bringing the cycle total to 12 units. To complete the 60 units of work, it takes exactly 5 such cycles, so the total time taken is 15 days.

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