Question

A work-force of 420 men with a contractor can finish a certain piece of work in 9 months. How many extra men must he employ to complete the job in 7 months?

Answer 1

Let x be the extra number of men employed to complete the job in 7 months.
 

Number of men	420	x
Months	9	7

\[\text{ Since the number of men hired and the time required to finish the piece of work are in inverse variation, we have } : \]
\[420 \times 9 = 7x\]
\[ \Rightarrow x = \frac{420 \times 9}{7}\]
\[ = 540\]
\[\text{ Thus, the number of extra men required to complete the job in 7 months }  = 540 - 420 = 120\]