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Saturday, 31 October

JEE Main 2021 · MathsMultiple choiceSingle correctMediumMulti-step

JEE Main 4 August 2021, Shift 2, Maths Q78

Question 78 of 90 in this shift, Maths question 18 of 30, Section A.

A bag contains four bulbs. Some of these bulbs are defective. Two bulbs are drawn at random and it is found that both the bulbs are defective. What is the probability that the bag contains exactly 3 defective bulbs?
  1. (1)0.5
  2. (2)0.3Official answer
  3. (3)0.6
  4. (4)0.75

Official answer

Option 2

NTA final key.

Chapter
Probability
Topic
Bayes' Theorem
Idea tested
Implicit Equally Likely Priors

Same idea in other shifts

Asked 2× in all
  1. 1 Feb 2024, Shift 1 · Q17A bag contains 8 balls, whose colours are either white or black. 4 balls are drawn at random without replacement and it was found that 2…MediumSingle 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.