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Saturday, 31 October

JEE Main 2021 · MathsMultiple choiceSingle correctMediumMulti-step

JEE Main 27 August 2021, Shift 1, Maths Q75

Question 75 of 90 in this shift, Maths question 15 of 30, Section A.

When a certain biased die is rolled, a particular face occurs with probability 16−x\frac{1}{6}-x and its opposite face occurs with probability 16+x\frac{1}{6}+x. All other faces occur with probability 16\frac{1}{6}. Note that opposite faces sum to 7 in any die. If 0<x<160<x<\frac{1}{6}, and the probability of obtaining total sum=7, when such a die is rolled twice, is 1396\frac{13}{96}, then the value of xx is :
  1. (1)19\frac{1}{9}
  2. (2)116\frac{1}{16}
  3. (3)112\frac{1}{12}
  4. (4)18\frac{1}{8}Official answer

Official answer

Option 4

NTA final key.

Chapter
Probability
Topic
Conditional Probability
Idea tested
Conditioning on Dice Sums

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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.