Question

A and B can do a piece of work together in 4 days while C and D can do the same work in 12 days. In how many days will A, B, C, and D do it together?

• A. 4 days
• B. 6 days
• C. 2 days
• D. 3 days

Answer 1

The correct option is D 3 days

Let the total work be 12 units.
A and B can do 3 units per day.
C and D can do 1 unit per day.
Thus, all four can do 4 units per day.
Hence, all four can finish the work in 3 days.