Multiple choice general knowledge math & puzzles

The smallest number which when diminished by 3 is divisible by 21,28,36 and 45 is...

  1. 869

  2. 859

  3. 1263

  4. 427
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C Correct answer
Explanation

We need N-3 to be divisible by 21, 28, 36, and 45. Therefore N-3 must equal the LCM of these numbers. LCM(21,28,36,45) = LCM(3×7, 2²×7, 2²×3², 3²×5) = 2² × 3² × 5 × 7 = 4 × 9 × 5 × 7 = 1260. So N = 1260 + 3 = 1263.

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