A and B work together. A alone can complete the work in 18 days and B alone in 28 days. What percentage of the total daily work is contributed by A? MCQ with Answer and Explanation

Explanation:
Total work = LCM(20, 30) = 60 units. Efficiency of A = +3, B = -2. In 2 days (A then B), net work done = 3 - 2 = 1 unit. We need to reach 60 units. Since A can add 3 units on his turn, we find when work reaches 60 - 3 = 57 units. 57 units will be done in 57 * 2 = 114 days. On the 115th day, A works and completes 3 units, making the total work 57 + 3 = 60 units. So, the wall is built in 115 days.

Explanation:
Using P1 * D1 * H1 = P2 * D2 * H2: 3 * 2 * 8 = 4 * 1 * H2 => 48 = 4 * H2 => H2 = 12 hours.

Explanation:
Remaining work = (1 - 5*(1/25+1/50))×100 = 70.0%.