A father is three times as old as his son. Five years ago he was four times as old. What is the son's present age?

  • A. 10 years
  • B. 15 years
  • C. 20 years
  • D. 12 years

Explanation

Let the son be x and the father 3x, so five years ago 3x minus 5 equals four times x minus 5, giving 3x minus 5 equals 4x minus 20 and x equal to 15. Checking, the father is now 45, and five years ago he was 40 against the son's 10, which is four times. Age problems are almost always solved with one variable and one equation.

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