One year ago a man was 7 times as old as his son. Now his age is equal to the square of his son's age. The present age of the man is :

Let the present age of man is 'm' and the present age of son is 's'

One year ago a man was 7 times as old as his son,

m - 1 = 7(s - 1) 

m = 7s - 6...........(1)

Present age of the man is equal to the square of his son's present age,

m = s$$^{2}$$.......(2)

Substitute equation (2) in equation (1)

s$$^{2}$$ = 7s - 6 (or)

s$$^{2}$$ - 7s + 6 = 0

After solving we get, s = 6 (or) 1  ('1' does not fit in the equation. Hence s = 6)

Son's age = 6 and fathers age = 36

Hence, option A is the correct answer.