Multiple choice

A mother tells his daughter 'I was half your present age when you were born'. If the mother is $18$ years older than her daughter, what is the present age of the mother ?

  1. $54$
  2. $63$
  3. $36$
  4. $72$
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A Correct answer
Explanation

Let the daughter's age be x. The mother's age is x + 18. When the daughter was born (age 0), the mother was x + 18 - x = 18. The problem states the mother was half the daughter's present age (x/2) when the daughter was born. So, x/2 = 18, which means x = 36. The mother's age is 36 + 18 = 54.

AI explanation

Let the daughter's present age be $x$ years. The mother was half of this, or $x/2$ years old, when the daughter was born. Therefore the age difference between mother and daughter is $x - x/2 = x/2$ years. Since the mother is 18 years older, $x/2 = 18$, meaning $x = 36$ is the daughter's current age. Adding 18 to 36 gives the mother's present age as 54 years.