In the series 6, 11, 21, X, 81, ..... the value of X is

If 1² + 2² + 3² + ... + n² = [n(n+1)(2n+1)] / 6, find the value of 5² + 6² + 7² + ... + 10².

Which term is wrong in the following series? 8, 13, 21, 32, 47, 63, 83

The missing number in the series is: 4, 18, 48, ?, 180

8th term of the following series will be : 2, 6, 18, 54, ...

Find wrong number in the series. 81, 225, 153, 189, 173, 180