Question

What is the sum of all odd numbers 10 to 55

Answer 1

To sum consecutive numbers we use the formula:

n * (n+1) / 2

1 through 55 = (55 * 56) / 2 = 1,540

1 through 9 = (9 * 10) / 2 = 45

10 through 55 = 1,540 -45 = 1,495

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EDITED

Gee, it seems I added ALL numbers from 10 through 55

ALL ODD numbers from 10 through 55 sum to

759

Explanation: