A can complete a work in 21 days and B in 42 days. After working together for 5 days, what percentage of work remains? MCQ with Answer and Explanation

Explanation:
Let B's efficiency = 1, then A's efficiency = 3. Combined efficiency = 3 + 1 = 4. Total work = 18 * 4 = 72 units. Time taken by A alone = 72 / 3 = 24 days.

Explanation:
Wages are distributed in the ratio of their efficiencies. Ratio of time taken = 12 : 15 : 20. Ratio of efficiencies = 1/12 : 1/15 : 1/20. Multiplying by LCM (60), we get 5 : 4 : 3.

Explanation:
Combined rate = 1/23 + 1/15. Required time = 9.08 days.