JEE Main 2021 · MathsNumerical answerNumerical valueMediumCalculation

JEE Main 31 August 2021, Shift 1, Maths Q88

Question 88 of 90 in this shift, Maths question 28 of 30, Section B.

An electric instrument consists of two units. Each unit must function independently for the instrument to operate. The probability that the first unit functions is 0.9 and that of the second unit is 0.8. The instrument is switched on and it fails to operate. If the probability that only the first unit failed and second unit is functioning is p, then

98\,\mathrm{p}

is equal to __________.

Official answer

NTA final key.

Chapter: Probability
Topic: Conditional Probability
Idea tested: Conditional Probability Definition

Same idea in other shifts

Asked 5× in all

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28 Jul 2022, Shift 1 · Q9Out of 60% female and 40% male candidates appearing in an exam, 60% candidates qualify it. The number of females qualifying the exam is…EasySingle correct
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26 Aug 2021, Shift 2 · Q78A fair die is tossed until six is obtained on it. Let X be the number of required tosses, then the conditional probability…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.