the given sequence is 101, 103, ….199

Given an AP whose first term a is 101, and common difference d is 2

To find: the sum of all odd numbers between 100 and 200

Hence the sum is given by the formula

Substituting the values in the above equation we get

Now for the finding number of terms, the formula is

Substituting n is the sum formula we get

s = 25 × 300

s = 7500