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Friday, 9 October

JEE Main 2025 · MathsMultiple choiceSingle correctMediumMulti-step

JEE Main 3 April 2025, Shift 2, Maths Q8

Question 8 of 75 in this shift, Maths question 8 of 25, Section A.

If the probability that the random variable XX takes the value xx is given by P(X=x)=k(x+1)3−x, x=0,1,2,3…P(X = x) = k(x + 1)3^{-x},\ x = 0, 1, 2, 3\ldots, where kk is a constant, then P(X≥3)P(X \geq 3) is equal to
  1. (1)727\frac{7}{27}
  2. (2)827\frac{8}{27}
  3. (3)49\frac{4}{9}
  4. (4)19\frac{1}{9}Official answer

Official answer

Option 4

NTA final key.

Chapter
Probability
Topic
Arithmetico-Geometric Series
Idea tested
Sum of Infinite AGP

Same idea in other shifts

Asked 2× in all
  1. 25 Jul 2021, Shift 1 · Q84If the value of…MediumNumerical value

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 42 of the 174 JEE Main shifts held from 2017 to 2026.