JEE Main 2023 · MathsNumerical answerNumerical valueHardCalculation

JEE Main 6 April 2023, Shift 2, Maths Q23

Question 23 of 90 in this shift, Maths question 23 of 30, Section B.

(20)^{19}+2(21)(20)^{18}+3(21)^2(20)^{17}+\ldots+20(21)^{19}=k(20)^{19}

, then

k

is equal to ___________.

Official answer

400

NTA final key.

Chapter: Binomial Theorem
Topic: Arithmetico-Geometric Series
Idea tested: Sum of Finite AGP

Same idea in other shifts

Asked 3× in all

11 Apr 2023, Shift 1 · Q25Let $S = 109 + \frac{108}{5} + \frac{107}{5^2} + \ldots + \frac{2}{5^{107}} + \frac{1}{5^{108}}$ . Then the value of $(16S - (25)^{-54})$ …MediumNumerical value
25 Jun 2022, Shift 2 · Q8The sum $1 + 2 \cdot 3 + 3 \cdot 3^2 + ....... + 10 \cdot 3^9$ is equal to :EasySingle correct

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.