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

asked Feb 9, 2013

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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

answered Feb 10, 2013 by Level 4 User (5,600 points)

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

answered Jan 23, 2016 by anonymous

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