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      Question

      What is the average of the squares of the first 31 natural

      numbers?
      A 324 Correct Answer Incorrect Answer
      B 330 Correct Answer Incorrect Answer
      C 336 Correct Answer Incorrect Answer
      D 342 Correct Answer Incorrect Answer

      Solution

      Sum of squares of first 'n' natural numbers = n × (n + 1) × (2n + 1) ÷ 6
      So, average = n × (n + 1) × (2n + 1) ÷ 6n = (n + 1) × (2n + 1) ÷ 6
      = (31 + 1) × (2 × 31 + 1) ÷ 6
      = 32 × 63 ÷ 6

      = 336

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