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      Question

      Find the smallest number which when divided by 7, 9 and

      12 leaves a remainder 5 in each case.
      A 257 Correct Answer Incorrect Answer
      B 239 Correct Answer Incorrect Answer
      C 247 Correct Answer Incorrect Answer
      D 263 Correct Answer Incorrect Answer

      Solution

      Let the number be N. N ≑ 5 (mod 7), (mod 9), (mod 12) β‡’ N βˆ’ 5 is divisible by 7, 9 and 12 LCM(7, 9, 12): 7 = 7 9 = 3Β² 12 = 2Β² Γ— 3 LCM = 2Β² Γ— 3Β² Γ— 7 = 4 Γ— 9 Γ— 7 = 252 So N βˆ’ 5 = 252 β‡’ N = 252 + 5 = 257

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