The present age of the father of a boy is twice the age of the boy. Six years later the ratio of their ages will be 11 : 6. Find the present age of the boy.

The boy is 30 years old now.

Let the boy be b, so the father is 2b.

Six years later, (2b + 6)/(b + 6) = 11/6.

6(2b + 6) = 11(b + 6) gives 12b + 36 = 11b + 66.

b = 30.

So the present age of the boy is 30.