A can complete a work in 13 days and B in 42 days. If both work together, in how many days will the work be 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:
Remaining work = (1 - 5*(1/23+1/46))×100 = 67.39%.

Explanation:
Combined rate = 1/15 + 1/26. Required time = 9.51 days.