Four men working together can do a ditch in 42 days. They begin, one man half days. How long will it take to complete

This is a classic work and time problem, which relies on the concept of total work units. First, calculate the total work required: 4 men working for 42 days equals 4 * 42 = 168 man-days of work. Next, determine the effective workforce under the new conditions. If three men work full days and one man works half days, the effective number of men is 3 + 0.5 = 3.5 men.

• To find the time taken, divide the total work by the effective workforce: 168 man-days / 3.5 men = 48 days (B).
• Options 45 days (A), 52 days (C), and 60 days (D) are incorrect calculations that do not account for the reduced work output of one man.