Question

A certain number of men can finish a piece of work in 100 days. However, if there were 10 men less, it would take 10 days more for the work to be finished. How many men were there originally?

Answer 1

Let the original number of men be x.

Days	Number of men
100	x
110	x - 10

Number of days and number of men are in inverse variation.
So, using arrow method:
$\frac{110}{100}=\frac{x}{x-10}$
On cross multiplication,
$100x=110(x-10)100x=110x-1100110x-100x=110010x=1100x=110$
So, the original number of men is 110.