Correct Answer - Option 2 : 38.5
Formula used:
The average of squares of first n natural numbers = [(n + 1)(2n + 1)]/6
Calculation:
Average = [(n + 1)(2n + 1)]/6
⇒ Average = [(10 + 1)(2 × 10 + 1)]/6
⇒ Average = (11 × 21)/6 = 231/6
⇒ Average = 231/6 = 38.5
∴ The average of 12 + 22 + 32 + 42 + ...... 102 is 38.5.