Maharashtra State BoardHSC Arts 12th Board Exam
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A Person Buys a Lottery Ticket in 50 Lotteries, in Each of Which His Chance of Winning a Prize is 1 100 . What is the Probability that He Will Win a Prize Exactly Once . - Mathematics and Statistics

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A person buys a lottery ticket in 50 lotteries, in each of which his chance of winning a prize is \[\frac{1}{100} .\]  What is the probability that he will win a prize exactly once.

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Let X denote the number of times the person wins the lottery. 
Then, X follows a binomial distribution with n = 50.

\[\text{ Let p be the probability of winning a prize } . \]

\[ \therefore p = \frac{1}{100}, q = 1 - \frac{1}{100} = \frac{99}{100}\]

\[\text{ Hence, the distribution is given by } \]

\[P(X = r) =^{50}{}{C}_r \left( \frac{1}{100} \right)^r \left( \frac{99}{100} \right)^{50 - r} , r = 0, 1, 2 . . . 50\] 
\[P(\text{winning exactly once}) = P(X = 1)\]

\[ = ^{50}{}{C}_1 \left( \frac{1}{100} \right)^1 \left( \frac{99}{100} \right)^{50 - 1} \]

\[ = \frac{1}{2} \left( \frac{99}{100} \right)^{49} \]

Hence, probability of winning a prize exactly once \[=\frac{1}{2} \left( \frac{99}{100} \right)^{49}\]

Concept: Bernoulli Trials and Binomial Distribution
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RD Sharma Class 12 Maths
Chapter 33 Binomial Distribution
Exercise 33.1 | Q 44.2 | Page 15

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