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Saturday, 31 October

JEE Main 2023 · MathsNumerical answerNumerical valueHardMulti-step

JEE Main 11 April 2023, Shift 2, Maths Q30

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

Let the probability of getting head for a biased coin be 14\frac{1}{4}. It is tossed repeatedly until a head appears. Let NN be the number of tosses required. If the probability that the equation 64x2+5Nx+1=064x^2 + 5Nx + 1 = 0 has no real root is pq\frac{p}{q}, where pp and qq are co-prime, then q−pq - p is equal to ________.

Official answer

27

NTA final key.

Chapter
Probability
Topic
Conditional Probability
Idea tested
Conditional Probability in Infinite Games

Same idea in other shifts

Asked 3× in all
  1. 29 Jan 2024, Shift 1 · Q19A fair die is thrown until 2 appears. Then the probability, that 2 appears in even number of throws, isMediumSingle correct
  2. 12 Apr 2023, Shift 1 · Q30A fair nn (n>1)(n>1) faces die is rolled repeatedly until a number less than nn appears. If the mean of the number of tosses required is…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 108 of the 174 JEE Main shifts held from 2017 to 2026.