JEE Main 2020 — Probability Question with Solution
From: JEE Main 2020 (Online) 5th September Evening Slot
Question
In a bombing attack, there is 50% chance that
a bomb will hit the target. Atleast two
independent hits are required to destroy the
target completely. Then the minimum number
of bombs, that must be dropped to ensure that
there is at least 99% chance of completely
destroying the target, is __________.
Enter your answer
Show full solutionCorrect answer: 11
Correct answer
11
Step-by-step explanation
Let n is total no. of bombs being dropped
at least 2 bombs should hit.
P(x > 2) 0.99
1 - p(x < 2) 0.99
1 - (p(x = 0) + p(x = 1)) 0.99
1 - nC0 - nC1. 0.99
1 - -
2n 100(n + 1)
Now checking for value of n, we get
n = 11
at least 2 bombs should hit.
P(x > 2) 0.99
1 - p(x < 2) 0.99
1 - (p(x = 0) + p(x = 1)) 0.99
1 - nC0 - nC1. 0.99
1 - -
2n 100(n + 1)
Now checking for value of n, we get
n = 11
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This is a previous-year question from JEE Main 2020, covering the Probability chapter of Mathematics. PrepSharp catalogues every PYQ from JEE Main with a verified answer key and step-by-step solution prepared by IIT alumni — so you can search by chapter, topic or year and revise efficiently.