On a playground, some men were playing football. In that group, 5 men were grandfathers of

someone else in the group, 15 men were fathers of someone else in the group and 15 men were

sons of someone else in the group. What is the minimum number of men on the playground?

n(A) = 5 grandfathers

 

Now, from 15 fathers, there is a possibility of 5 grandfathers,

So, n(B)= 15- n(A) = 10 fathers

 

But from 15 fathers, there is a possibility of 5 sons which we will be excluding from the 15 sons.

So, n(C)= 15- n(B)= 10 sons

 

So, total number of men playing fotball= 5+10+10=25