CTET Class I to V 2015 Feb Paper

Question : 58 of 150

Marks: +1, -0

What is the value of – 1 + 2 – 3 + 4 – 5 + 6 – 7 + ... + 1000?

Solution:

Grouping the first and second numbers, third and fourth number, fifth and sixth numbers and so on
we get 500 pairs of number

=(-1+2)+(-3+4)+(-5+6) . . . . .+(-997+998)+

(-995+100)=1+1+. . . . . . . . . .+1+1=500

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