A can do a job in 10 days and B in 12 days. They work on alternate days starting with A. In how many days will the job be finished?
Show answer & explanation
Correct answer: C
Explanation
Given:
A works alone = 10 days
B works alone = 12 days
Work is done on alternate days (A first)
A's rate per day = 1/10
B's rate per day = 1/12
Work done in 2 days = 1/10 + 1/12 = 11/60
Work done in 10 days (5 cycles) = 5 × 11/60 = 55/60
= 11/12
Remaining work = 1 − 11/12 = 1/12
Now A will work
A's rate = 1/10
Time = (1/12) ÷ (1/10) = 10/12 = 5/6 days
Total time = 10 + 5/6 = 10⅚ days