A can complete a work in 28 days and B in 32 days. If both work together, in how many days will the work be completed? MCQ with Answer and Explanation

Explanation:
Combined rate = 1/19 + 1/19. Time = 9.5 days.

Explanation:
Remaining work = (1 - 5*(1/24+1/48))×100 = 68.75%.

Explanation:
Total work = LCM(12, 15, 20) = 60 units. Efficiency of (A+B) = 5, (B+C) = 4, (C+A) = 3. Summing efficiencies gives 2*(A+B+C) = 12 => Efficiency of (A+B+C) = 6 units/day. Efficiency of A = (A+B+C) - (B+C) = 6 - 4 = 2 units/day. Time taken by A alone = 60 / 2 = 30 days.