ANSWER: 10,000

EXPLANATION:
The first 100 odd numbers form a series: 1,3,5,7,9...191,193,195,197,199. To determine the sum of all of the numbers in this series, pair off the first and last number, etc., which yields (1 and 199), (3 and 197), (5 and 195)...(97 and 103) and (99 and 101). Notice that the sum of each pair is 200. Since there are 100 numbers, there are 50 pairs; therefore, the sum is 200 times 50, or 10,000.

BONUS! The sum of the first million odd numbers is one trillion or 1,000,000,000,000!!!