Five years ago, the ratio of the ages of A and B was 3 : 4. Five years from now,the ratio of their ages will be 4 : 5. What is the ratio of A and B, 10 years from now?

9 : 11

Ratio of age 5 years ago,

A : B

3 : 4

Ratio of age 5 years from now,

A : B

4 : 5

⇒ (4 - 3) units = 10

⇒ 1 unit = 10 years,

⇒ Present age = 4 x 10 - 5 : 5 x 10 - 5

⇒ 35 : 45

⇒ The ratio of A and B, 10 years from now = 35 + 10 : 45 + 10 = 45 : 55 = 9 : 11.