Question

Find the sum of this series

Answer 1

Answer:

2485

Step-by-step explanation:

Given Series is (11² + 12² + 13² + ... +20²).

It can be written as:

⇒ (1² + 2² + 3² + ... + 20²) - (1² + 2² + 3² + ... + 10²).

Sum of squares of first n natural numbers = n(n + 1)(2n + 1)/6.

Here, n = 20, 10.

⇒ [20(20 + 1)(40 + 1)/6] - [10(10 + 1)(20 + 1)/6]

⇒ [2870] - [385]

⇒ 2485.

Therefore, the sum of series is 2485.

Hope this helps!