To solve this problem, we first determine the total amount of work required in man-hours. Initially, 105 men working for 8 hours a day over 50 days amounts to a total work of:
\( \text{Total Work} = 105 \times 8 \times 50 \).
This results in 42,000 man-hours required to complete the work.
After 25 days, it is given that \(\frac{2}{5}\) of the work is finished. Hence, the work completed in 25 days is:
\( \text{Work Done} = \frac{2}{5} \times 42,000 = 16,800 \) man-hours.
The remaining work then is:
\( \text{Remaining Work} = 42,000 - 16,800 = 25,200 \) man-hours.
Now, we need to complete 25,200 man-hours of work in the remaining 25 days with increased working hours of 9 hours a day. The new condition requires us to determine how many men are needed to satisfy:
\( \text{Remaining Work} = \text{Number of Men} \times 9 \times 25 = 25,200 \).
Let \( x \) be the number of additional men required. The equation becomes:
\( (105 + x) \times 9 \times 25 = 25,200 \).
Solving for \( x \), we substitute and simplify:
\( (105 + x) \times 225 = 25,200 \)
\( 105 + x = \frac{25,200}{225} \)
\( 105 + x = 112 \)
\( x = 112 - 105 \)
\( x = 7 \).
Therefore, 7 additional men are needed. Adding options verification, since the question requires additional men for on-time completion without specifying the standard reduction to 9 hours, considering increased need, determines options needing further exploration.
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