Multiple choice

Five years ago, a father's age was three times the age of his son. Five years from now, the father's age will be double his son's age. Find the sum of their present ages.

  1. 45

  2. 50

  3. 28

  4. 70

  5. 17
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Let F and S be current ages. (F-5) = 3(S-5) implies F = 3S - 10. (F+5) = 2(S+5) implies F = 2S + 5. Equating them: 3S - 10 = 2S + 5, so S = 15 and F = 35. The sum is 15 + 35 = 50.

AI explanation

Let the son's present age be S and the father's present age be F. The first condition yields F - 5 = 3(S - 5), simplifying to F = 3S - 10. The second condition yields F + 5 = 2(S + 5), simplifying to F = 2S + 5. Equating the two gives 3S - 10 = 2S + 5, meaning S is 15, and substituting S gives F as 45, so their combined present age is 50.

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