Answer:
Option B
Explanation:
Let the required number of hours be x.
Speeds of working of first and second type of men are \frac{1}{2} and \frac{1}{3}
More work, More time (Direct Proportion)
Less speed, More time (Indirect Proportion)
\left\{\begin{array}{c}Work\quad 1:2\\ Speed\quad \frac{1}{3}:\frac{1}{2}\end{array}\right\}::25:x
\therefore\left(1\times\frac{1}{3}\times x\right) =\left(2\times\frac{1}{2}\times 25\right)
\Leftrightarrow x=75