To solve this problem, we calculate the total work in man-days and then find how many men are needed to finish it in 15 days.
Step 1: Calculate the total work.
One man completes the work in 60 days, so:
\[\text{Total Work} = 60 \times 1 = 60 \text{ man-days}\]
Step 2: Set up the equation for 15 days.
Let \(x\) be the number of men required. The total work done in 15 days by \(x\) men is:
\[15 \times x = 60\]
Step 3: Solve for \(x\).
\[x = \frac{60}{15} = 4\]
Thus, 4 men are needed to complete the work in 15 days.
Takeaway: For work problems, multiply men × days to get total work. Then divide total work by the new number of days to find how many men are required.