In order to get at least once a head with probability ge 0.9, number of times a coin needs to be tos

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14.Probability

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In order to get at least once a head with probability $ \ge 0.9,$ the number of times a coin needs to be tossed is

A

$3$

B

$4$

C

$5$

D

None of these

Solution

(b) Probability of getting at least one head in $n$ tosses

$ = 1 – {\left( {\frac{1}{2}} \right)^n} \ge 0.9 $

$\Rightarrow {\left( {\frac{1}{2}} \right)^n} \le 0.1 $

$\Rightarrow {2^n} \ge 10 \Rightarrow n \ge 3$

Hence least value of $n = 4.$

Standard 11

Mathematics

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