A and B working separately can finish the work in 18 days and 24 days, respectively. A begins the work and works for two consecutive days, while B works on the 3rd day. This pattern is continued till the work is completed. In how many days will the work be completed?
Show answer & explanation
Correct answer: C
Explanation
The correct answer is option 3 i.e. 19.
LCM(18, 24) = 72
The efficiency of A = 72/18 = 4 units
The efficiency of B = 72/24 = 3 units
Work done in three days = 4 + 4 + 3 = 11 units
Work done in 18 days = 66 units
Remaining = 72 - 66 = 6 units
Day 19 (A) does 4 units, Remaining = 2 units
Day 20 (A) needs 2/4 = 0.5 day
Total time = 18 + 1 + 0.5 = 19.5 days