Find the average of the squares of the consecutive odd numbers from 1 to 21.

A102

B159

C161 ✓ Correct

D160

Correct answer: (C) 161

Explanation

The required average is 161.

Odd numbers 1 to 21 are 11 terms.

Sum of their squares = n(2n-1)(2n+1)/3 with n = 11.

Sum = 11 x 21 x 23 / 3 = 1771.

Average = 1771 / 11 = 161.

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