Multiple choice

7 year ago the ratio of age (in year) of A and B was 4 : 5 and after 7 year this ratio become 5 : 6 . Find the present age of B?

  1. 56 year

  2. 63 year

  3. 70 year

  4. 77 year

Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Let present ages of A and B be x and y. 7 years ago: (x-7)/(y-7) = 4/5. After 7 years: (x+7)/(y+7) = 5/6. Solving: 5(x-7) = 4(y-7) → 5x-35 = 4y-28 → 5x-4y = 7. Also 6(x+7) = 5(y+7) → 6x+42 = 5y+35 → 6x-5y = -7. Solving gives y = 77 years present. Option D is correct.