X and Y together can do a piece of work in 30 days. Z alone can do it in 60 days. If they worked together, then in how many days they can finish the work?
Show answer & explanation
Correct answer: D
Explanation
The correct answer is option 4 i.e. 20 days.
Concept used:
Total work = time × efficiency
Calculations:
Total work done (LCM of 30 and 60) = 60 units
Efficiency of X and Y = 60/30 = 2
Efficiency of Z = 60/60 = 1
Total efficiency of X + Y + Z = 3
Required time taken = 60/3 = 20 days