If the number of observations is odd, the number in the middle of the list is the median. This can be found by taking the value of the (n+1)/2 -th term, where n is the number of observations. Else, if the number of observations is even, then the median is the simple average of the middle two numbers.

To find the sum of first n odd numbers we can use the formula S_n= n². For example, to calculate the sum of odd numbers between 1 to 10, we know that n = 5. Thus, S₅ = 5² = 25.