Answer:
5050
Explanation:
The sum of an arithmetic series is the product of the number of terms and the average value of a term. That average value can be found as the average of the first and last terms. Then for (a1 + a100) = 101, the average term is ...
(a1 +a100)/2 = 101/2 = 50.5
Since there are 100 terms, the sum of them is ...
100 × 50.5 = 5050
The sum of the first 100 terms is 5050.