Multiple choice

A mother tells his son, "I was of your present age when you were born". If the mother is now $36,$ how old was his son $5$ years ago?

  1. $13$
  2. $15$
  3. $17$
  4. $20$
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A Correct answer
Explanation

Let son's age be x and mother's be y. Mother was x when son was 0. Difference in age is x. Now y = 36. Since y = 2x (mother is twice the son's age), x = 18. Five years ago, son was 18 - 5 = 13.

AI explanation

Let the son's present age be x years. The mother is 36 years old now, so her age when the son was born was 36 minus x, which equals the son's present age x. Solving 36 minus x equals x gives x equals 18. Five years ago the son was 18 minus 5 which is 13 years old.

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