A can complete a job in 36 days. Every third day, he is assisted by B who can complete the job alone in 48 days. In how many days will the job be completed?
Show answer & explanation
Correct answer: C
Explanation
A's work in 1 day = 1/36
B's work in 1 day = 1/48
First day → A = 1/36
Second day → A = 1/36
Third day → A + B = 1/36 + 1/48
Total work -
= 1/36 + 1/36 + 1/36 + 1/48
= 3/36 + 1/48
= 1/12 + 1/48
= 5/48
Work done in 27 days (9 cycles) -
= 9 × 5/48
= 45/48
= 15/16
Remaining work = 1/16
Work done by A alone = (1/16) ÷ (1/36)
= 36/16 = 2 1/4 days
Total time = 27 + 2 1/4 ≈ 29 1/7 days