Multiple choice

The ratio of present ages of two persons, A and B is 3 : 4. After 20 years, this ratio will become 7 : 8. What is the present age of A?

  1. 12 years

  2. 15 years

  3. 24 years

  4. 27 years

  5. 30 years
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Let ages be 3x and 4x. (3x+20)/(4x+20) = 7/8. 24x + 160 = 28x + 140. 4x = 20, x = 5. Present age of A = 3x = 15.

AI explanation

Let the present ages of A and B be 3x and 4x respectively. After 20 years, their ages will be 3x + 20 and 4x + 20, so we write the proportion (3x + 20) / (4x + 20) = 7 / 8. Cross-multiplying gives 24x + 160 = 28x + 140, which simplifies to 4x = 20 and x = 5. Therefore, the present age of A is 3 multiplied by 5, which is 15 years.

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