Probability 5 Question 7

7. Two cards are drawn successively with replacement from a well shuffled deck of 52 cards. Let X denote the random variable of number of aces obtained in the two drawn cards. Then, P(X=1)+P(X=2) equals

(a) 25169

(b) 52169

(c) 49169

(d) 24169

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Answer:

Correct Answer: 7. (a)

Solution:

  1. Let p= probability of getting an ace in a draw = probability of success

and q= probability of not getting an ace in a draw = probability of failure

Then, p=452=113

and q=1p=1113=1213

Here, number of trials, n=2

Clearly, X follows binomial distribution with parameter n=2 and p=113.

Now, P(X=x)=2Cx113x12132x,x=0,1,2

P(X=1)+P(X=2)

=2C111311213+2C2113212130

=212169+1169

=24169+1169=25169



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