Multiple choice

The age of a man is $3$ times that of his son. $15$ years ago, the man was $9$ times as old as his son. What will be the age of man after $15$ years?

  1. $60$ years
  2. $80$ years
  3. $75$ years
  4. $105$ years
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Let son's age be x, man's age 3x. 15 years ago: 3x-15 = 9(x-15). 3x-15 = 9x-135, 6x = 120, x = 20. Man's current age = 60. After 15 years, he will be 75.

AI explanation

Let the son's present age be x, making the man's present age 3x. Fifteen years ago, their ages were x - 15 and 3x - 15, which gives the equation 3x - 15 = 9(x - 15). Solving yields 3x - 15 = 9x - 135, meaning 6x = 120 and x = 20. The man's present age is 60, so after 15 years he will be 75 years old.

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