2024 · Q20
A, B, C, D can complete a work in 3, 6, 9, 12 hours respectively. Further, only one person can work at a time in each hour and nobody can work for two consecutive hours. It is not necessary to engage all. What is the minimum number of hours that they will take to finish the work?
Elementary MathematicsTime and Work
- A36/25
- B12/5
- C4
- D2
Explanation
A fills 1/3 and B fills 1/6 of the tank per hour. Alternating A, B, each two-hour block completes 1/3 + 1/6 = 1/2 of the tank, so two blocks (4 hours) finish it. Since A and B are the two fastest pipes, 4 hours is minimal, option (c).