A, B and C can complete a piece of work in 12, 20 and 15 days, respectively. A, B and C will complete the work while working on alternate days. C works on the 1st day, B works on the 2nd day and A works on the 3rd day and so on. In how many days will the work get complete?
Show answer & explanation
Correct answer: C
Explanation
The correct answer is option 3 i.e. 15 .
A's 1-day work = 1/12
B's 1-day work = 1/20
C's 1-day work = 1/15
Work pattern: Day 1 = C, Day 2 = B, Day 3 = A → repeats every 3 days.
Work in 3 days = C + B + A
= 1/15 + 1/20 + 1/12
LCM = 60 → (4 + 3 + 5)/60 = 12/60 = 1/5
So, in 3 days → 1/5 of work done
Total work = 1
Time = 3 × 5 = 15 days