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Joint Entrance Examination
Mathematics
Probability
Question 222
Question 222 of 417
Easy
MCQ
Find the minimum number of tosses of a fair coin so the probability of at least one head is
≥
90
%
\ge90\%
≥
90%
.
A
5
B
3
C
4
D
2
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Official solution
\[1-\left(\frac12\right)^n \ge 0.9 \implies \left(\frac12\right)^n\le0.1 \implies n\ge4\]
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