Seven years ago, the ratio of the ages of A and B was 4 : 5. Eight years hence, the ratio of the ages of A and B will be 9 : 10. What is the difference between their present ages in years?

3

Lets assume,

Age of A, 7 years ago = 4x

Age of B , 7 years ago = 5x

Ratio of ages of A and B , 8 years hence = \(\frac{4x+ 7 + 8}{5x+ 7 + 8}\) = \(\frac{9}{10}\)

⇒ 40x + 150 = 45x + 135

⇒ x = 3

Present age of A = 19

Present age of B = 22

Difference b/w present age of A and B = 3 years