A's age is the 6th part of his father's age.  After 16 years the age of A's father will be twice the age of B.  If B's 10th birthday is celebrated 25 years ago, then what is the present age of A?

9 10 8 11

9

B's present age = 10 + 25 = 35 years A's father age 16 years after = 35 × 2 = 70 years A's father present age = 70 - 16 = 54 years A's age = 54 × \(\frac{1}{6}\) = 9 years