Multiple choice general knowledge math & puzzles

Grandpa: "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 140 years. Can you tell me my age in years?"

  1. 86

  2. 84

  3. 88

  4. 90

  5. 92
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Let grandson be G, son be S, grandpa be J. G days = S weeks -> G = 7S (incorrect logic, should be G = S/7). Correct logic: G = S/7 and G = J/12. J + S + G = 140. J + 12G/7 (wait) -> G = J/12, S = 7G. J + 7G + G = 140 -> 12G + 7G + G = 140 -> 20G = 140 -> G = 7. J = 12 * 7 = 84.

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