What's 1+2+3+4+5+6+7+8+9+10?

Question

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Answer 1

use Gaus' method

Sum = n(n+1)/2

if n= 10 then

sum = 10(11)/2 = 55

or just add them all up

1+2+3+4+5+6+7+8+9 + 10, punch them into a calculator or

pair the 1st & last, 2nd & 2nd to last, 3rd & 3rd to last, 4th and 4th to last, + 5th & 5th to last

(1+10) + (2+9) + (3+8) + (4+7) + (5+6) = 11 + 11 + 11 + 11 +11 = 5 x 11 = 55