If 10 men can complete a piece of work in 30 days how many men are requiredto complete the same job in 25 days?

We must assume that all workmen work at the same rate, and keep it up forever.

More men = = > fewer days

so the proportion is: 30/25 = x/10

Cross-multiply the proportion:

300 = 25 x

Divide each side by 25:

x = 300/25 = 12 men