What is the sum of all the odd numbers from 1 to 9?

Sum of all the odd numbers from 1 to 9

To calculate the sum of all the odd numbers from 1 to 9, we simply add up all the odd numbers from 1 up to 9.

When we add up 1 + 3 + 5 ... all the way to 9, we get the following answer:

25

What we find interesting is that when you add up all the odd numbers from 1 to any number, the sum will always be a perfect square.

The sum of odd numbers from 1 to 9 is no exception. To prove that the result is a perfect square, the square root of the result above should be an integer (whole number), which it is:

√25 = 5

To summarize, the sum of all the odd numbers from 1 to 9 is 25 and the sum is a perfect square.

Sum of Odd Numbers Calculator
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Sum of all the odd numbers from 1 to 10
Another sum of odd numbers we have calculated.