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Mon 17 Feb, 2003 05:23 am
What is the sum of all fields on a chessboard, 1-64? 1+2+3+4+...etc. There are two solutions to this riddle, if you know the answer, please show us which solution you used.
(2^64) -1 = 18446744073709551615
Laura
This one wasn't fair and Laura didn't get it either. Either you spend half an hour adding 1, 2, 3, etc. or you use calculus to see it's 2080.
TiGeR
O yes, I must have been sleeping. Yes that's it
sleeping, yep, I know. Dreaming. ... e ahem.
Laura
Half day adding is too much, TGR, lol! But yup, 2080 is right....
You use summation (the capital sigma with an n=1 and 64 on the top follow by an n)...
TiGeR
Easy
64 squares so there will be 32 pairs, the sum of each pair (first plus last, second plus second to last, third plus third to last) is 65.
65 x 32 = 2080
QED
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