Multiple choice

Eighteen years ago, the ratio of A's age to B's age was 8 : 13. The ratio of their present ages is 5 : 7. What is the present age of A?

  1. 60 years

  2. 70 years

  3. 50 years

  4. 40 years
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Let present ages be 5x and 7x. 18 years ago, (5x - 18) / (7x - 18) = 8 / 13. 65x - 234 = 56x - 144. 9x = 90, so x = 10. A's present age is 5 * 10 = 50.

AI explanation

Let their present ages be 5x and 7x, meaning 18 years ago their ages were 5x - 18 and 7x - 18. This gives the equation (5x - 18) / (7x - 18) = 8 / 13, so 13(5x - 18) = 8(7x - 18). Expanding results in 65x - 234 = 56x - 144, which means 9x = 90 and x = 10. A's present age is 5x, which equals 50 years.

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