Question 234983
1-2 + 3 -4 + ....-98 + 99 equals 
a) -50 b) -49 c) 0 d) 49 e) 50
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There are 99 numbers.
Put them in pairs, 
1+99 = 100
-2-98 = -100
... 
49+51 = 100  It's all even, at zero, to this point
Then the -50 has nothing to pair with
--> = -50