Multiple choice

Ratio of age of son and father is (1 : 6). After 15 years, this ratio becomes (4 : 9). What is the ratio of their ages after 30 years from now?

  1. $5 : 12$
  2. $7 : 12$
  3. $3 : 12$

  4. None of the above
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Let ages be x and 6x. After 15 years: (x+15)/(6x+15) = 4/9. Solving gives 9x+135 = 24x+60, so 15x = 75, x = 5. Current ages: 5 and 30. After 30 years: 35 and 60, ratio 35:60 = 7:12.

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