Multiple choice general knowledge math & puzzles

"My grandson is about as many days as my son is weeks, and my grandson is as many months as I am in years. My grandson, my son and I together are 100 years. Can you tell me my age in years?"

  1. 78

  2. 80

  3. 50

  4. 60
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Let grandson's age be g, son's age be s, and your age be y. Grandson's days = son's weeks means g*365 = s*52, so g ≈ s/7. Grandson's months = your years means g*12 = y. Also g + s + y = 100. Substituting y = 12g and s ≈ 7g: g + 7g + 12g = 100, so 20g = 100, g = 5. Therefore y = 12*5 = 60 years.

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