Question

Q 1-2+3-4+5-6+.....+179-180

Answer 1

1-2=-1

3-4=-1

5-6=-1

.

.

.

.

179-180=-1

=-1-1-1-1....

=-1×180

=-180

Answer 2

S =   1 - 2 + 3 - 4 + 5 - 6 + ___ + 179 - 180

+   S =       1 - 2 + 3 -  4 + 5 - 6 + ___ + 179 - 180

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2S =           1 - 1 - 1 - 1 - 1 - 1 - 1 - 1 - ___ - 1 - 1 - 1 - 180

2S = -180

S =   $\frac{-180}{2}$

S = -90