A can finish a work in 12 days and B can do it in 15 days. After A had worked for 3 days, B also joined him to finish the remaining work. In how many days was the remaining work completed? MCQ with Answer and Explanation

Explanation:
Total work = LCM(20, 30, 60) = 60 units. Efficiency of A = 3, B = 2, C = 1. Day 1: A works (3 units). Day 2: A works (3 units). Day 3: A, B, and C work together (3 + 2 + 1 = 6 units). Total work in 3 days = 3 + 3 + 6 = 12 units. To complete 60 units, number of 3-day cycles needed = 60 / 12 = 5 cycles. Total days = 5 * 3 = 15 days.

Explanation:
Using M1 * D1 = M2 * D2: 12 * 36 = 18 * D2 => D2 = (12 * 36) / 18 = 12 * 2 = 24 days.

Explanation:
Total work = 624 man-days. Time = 624/29 = 21.52 days.