Sum of the first 100 odd numbers "The sum of the first 100 odd numbers" means that we want to add together the first 100 positive odd numbers. The list of the first 100 odd numbers starts with 1 and ends with 199. Thus, this is what we know:

Numbers = 100
First = 1
Last = 199

Below is the formula, calculation, and answer to "the sum of the first 100 odd numbers?":

(Numbers/2) x (First + Last)
(100/2) x (1 + 199)
= 10000

The method above requires us to first figure out what the last number is on the list of the first 100 odd numbers. We like the formula method above, but there is an alternate faster way to add up odd numbers. You can get the answer fast by squaring the number. Once again, the sum of the first 100 odd numbers is:

1002 = 10000

Sum of Odd Numbers Calculator
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What is the sum of the first 101 odd numbers?
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