Medium MCQ +4 / -1 PYQ · JEE Mains 2020

The value of (2.1P0 – 3.2P1 + 4.3P2 .... up to 51th term)
+ (1! – 2! + 3! – ..... up to 51th term) is equal to :

  1. A 1
  2. B 1 + (51)!
  3. C 1 – 51(51)!
  4. D 1 + (52)! Correct answer

Solution

(2.<sup>1</sup>P<sub>0</sub> – 3.<sup>2</sup>P<sub>1</sub> + 4.<sup>3</sup>P<sub>2</sub> .... up to 51<sup>th</sup> term)<br> + (1! – 2! + 3! – ..... up to 51<sup>th</sup> term) <br><br>= ( 2.1! - 3.2! + 4.3! - ....+ 52.51!) <br>+ ( 1! – 2! + 3! – ..... + (51)! ) <br><br>= (2! - 3! + 4! .....+ 52! ) <br>+ ( 1! - 2! + 3! - 4! + .....+ 51! ) <br><br>= 1 + (52)!

About this question

Subject: Mathematics · Chapter: Permutations and Combinations · Topic: Fundamental Counting Principle

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