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Two-condition age puzzle (father and son): Solve simultaneous relations to find the son's age. Now: Father's age = 3 × son's age. Five years ago: Father's age = 4 × son's age. Find the son's present age (in years). Choose the correct value.

Q: Two-condition age puzzle (father and son): Solve simultaneous relations to find the son's age. Now: Father's age = 3 × son's age. Five years ago: Father's age = 4 × son's age. Find the son's present age (in years). Choose the correct value.

Let Son = s, Father = 3s. Translate the past condition Five years ago: (3s − 5) = 4(s − 5). Solve 3s − 5 = 4s − 20 ⇒ −5 + 20 = 4s − 3s ⇒ s = 15. Check Now: Father = 45, Son = 15. Five years ago: 40 and 10 ⇒ 40 = 4 × 10 ✔

Difficulty: Easy

Correct Answer: 15

Explanation:

Let
Son = s, Father = 3s.

Translate the past condition
Five years ago: (3s − 5) = 4(s − 5).

Solve
3s − 5 = 4s − 20 ⇒ −5 + 20 = 4s − 3s ⇒ s = 15.

Check
Now: Father = 45, Son = 15. Five years ago: 40 and 10 ⇒ 40 = 4 × 10 ✔

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