The age of Arvind?s father is 4 times of his age. If 5 years ago, father's age was 7 times of the age of his son, what is the age of Arvind's father at present?

Explanation Option [b] is correct. Let the age of Arvind and his father be x and 4x years, respectively. Five years ago/the age of Arvind was (x ? 5) years and that of his father was (4x ? 5) years. Now, according to the information given in the question, or       (4x−5)=7(x−5) or      4x−5=7x−35 3x=30      or    x=10years Therefore, the age of Arvind and his father are 10 years and 40 years, respectively.