Medium MCQ +4 / -1 PYQ · JEE Mains 2021

If [x] be the greatest integer less than or equal to x,

then $\sum\limits_{n = 8}^{100} {\left[ {{{{{( - 1)}^n}n} \over 2}} \right]}$ is equal to :

  1. A 0
  2. B 4 Correct answer
  3. C $-$2
  4. D 2

Solution

$\sum\limits_{n = 8}^{100} {\left[ {{{{{( - 1)}^n}n} \over 2}} \right]}$<br><br>= [4] + [-4.5] + [5] + [-5.5] + [6] +..... + [-49.5] + [50] <br><br>= 4 - 5 + 5 - 6 + 6 ......-50 + 50 <br><br> = 4

About this question

Subject: Mathematics · Chapter: Complex Numbers and Quadratic Equations · Topic: Quadratic Equations

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