Question

If 36 men can do a piece of work in 25 hours, in how many hours will 15 men do it ?

Answer 1

Let the required number of hours be x. Then, 

Less men, More hours (Indirect Proportion) 

15 : 36 : : 25 : x 

(15 x x) = (36 x 25) 

(36 x 25)/15 = 60 

Hence, 15 men can do it in 60 hours.