What is the sum of the odd numbers from 1 to 73 (including 73)?
What is the sum of the odd numbers from 1 to 231?
N =(L - F) / D +1, where N=Number of terms, L=Last term, F=First term, D=Common difference.
N=(73 -1) / 2 + 1
N =37 terms
Sum = (F + L) / 2 x N
Sum = (1 + 73) / 2 x 37
Sum =1,369
Do exactly the same thing with numbers 1 to 231. If you don't make any mistakes, you should get:
Sum =13,456