The ages of A and B are in the ratio 4 : 9. If the difference of their ages is 10 years, compare their ages after 4 years from now.

Correct option is C

Given:
Ages of A and B are in the ratio 4 : 9 
Difference of their ages = 10 years
Solution:
Let the age of A and B are 4x and 9x
Difference between their ages = 10 
9x- 4x = 10 
5x = 10 
x = 2
So, Present age of A and B are 4$$\times 2 = 8$$ years and $$9 \times 2= 18$$ years
After 4 years, their ages will be 
A's age = 8 + 4 = 12 years 
B's age = 18 + 4 = 22 years 
Ratio = 12: 22 = 6: 11