JEE Main 2020 · MathsMultiple choiceSingle correctMediumApplication

JEE Main 4 September 2020, Shift 1, Maths Q55

Question 55 of 75 in this shift, Maths question 5 of 25.

The value of

\sum_{r=0}^{20} {}^{50-r}C_6

is equal to :

(1) ${}^{50}C_6 - {}^{30}C_6$
(2) ${}^{50}C_7 - {}^{30}C_7$
(3) ${}^{51}C_7 - {}^{30}C_7$ Official answer
(4) ${}^{51}C_7 + {}^{30}C_7$

Official answer

Option 3

NTA final key (Sep 2020).

Chapter: Binomial Theorem
Topic: Binomial Coefficients
Idea tested: Hockey Stick Identity

Same idea in other shifts

Asked 4× in all

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Question text from the official JEE Main paper published by NTA; answer from the final answer key. Chapter, topic and idea tags, difficulty and skill are Lumi’s. Lumi analyses 108 of the 174 JEE Main shifts held from 2017 to 2026.