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.**