Question

1-2 3-4 5-6 .... 179-180 calculate for class 6

Answer 1

rewrite this AP as
then,find n of each AP
$1 + (n - 1)2 = 179 \\ n = 90$
then,
$2 + (n - 1)2 = 180 \\ n = 90$



$(1 + 3 + 5upto179) - (2 + 4 + 6upto180)$
$45(1 + 179) - 45(2 + 180) = 45(1 + 179 - 2 - 180) = - 90$

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