Multiple choice

The ratio of the present age of A to that of B is 7 : 9. If the ratio of the age of A five years from now to that of B five years ago be 3 : 1, find the ratio of the age of A to that of B three years from now.

  1. 6 : 5

  2. 7 : 9

  3. 9 : 7

  4. 5 : 6

  5. 1 : 9
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Let ages be 7x and 9x. (7x+5)/(9x-5) = 3/1. Solving gives 7x+5 = 27x-15, so 20x = 20, x=1. Ages are 7 and 9. Three years from now, ages are 10 and 12. Ratio is 10:12 = 5:6.

AI explanation

Let the present ages of A and B be 7x and 9x respectively. According to the given condition, (7x + 5) / (9x - 5) = 3 / 1, which simplifies to 7x + 5 = 27x - 15. Solving this equation yields 20 = 20x, so x equals 1. The present ages of A and B are 7 years and 9 years respectively, making their ages three years from now 10 years and 12 years. The required ratio is 10 : 12, which simplifies to 5 : 6.

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