400 Men Have Provisions For 23 Weeks

400 men have provisions for 23 weeks. They are joined by 60 men. How long will the provisions last ?

Answers:

400 men have provisions for = 23 weeks
1 man will have provisions for = 23 x 400 weeks
and 400 + 60 = 460 men will have provisions for = \frac { 23 x 400 }{ 460 } weeks = 20weeks