use summation formula for AP S=(n/2)(2a+(n-1)d)
where a is the first term of the series, n is the number of terms
in the series and d is the common difference
for example, find the sum of odd numbers from 1 to 30. there are 15
terms in the odd no. series. the series is an AP therefore can use
the above formula coz 1,3,5,7,9....... common difference is 2
sub in the formula should get the ans 225
