What is the sum of the first 20 consecutive odd numbers?

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the first 20 consecutive odd numbers are:

1 + 3 + 5 + 7 + 9 + 11 + 13 + 15 + 17 + 19 + 21 + 23 + 25 + 27 + 29 + 31 + 33 + 35 + 37 + 39 = **400**

above are the first 20 odds

If you add the first to the last you get 40

If you add the second to the second from last you get 40

It doesn't matter which numbers you add first so long as you add them all up

there are 10 pairs of numbers totaling 40 so the sum is 400

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