X, Y and Z can complete a piece of work in 20, 12 and 28 days, respectively. If all work together, the approximate number of days to complete the work will be:
Show answer & explanation
Correct answer: A
Explanation
The correct answer is option 1 i.e. 6.
Total work = 420 (LCM of 20, 12, 28)
Efficiency of X = 420/20 = 21 units/day
Efficiency of Y = 420/12 = 35 units/day
Efficiency of Z = 420/28 = 15 units/day
Total efficiency = 21 + 35 + 15 = 71 units/day
Time required for X, Y, and Z = 420/71 = 5.91... = 6 days
Therefore, X, Y, and Z can complete the work in 6 days.