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Probability

Question
CBSEENMA12033656

A fair coin and an unbiased die are tossed. Let A be the event ‘head appears on the coin’ and B be the event ‘3 on the die’. Check whether A and B are independent events or not.

Solution

S = {(H, 1), (H, 2), (H, 3), (H, 4), (H, 5), (H, 6), (T, 1), (T, 2), (T, 3), (T, 4), (T, 5), (T, 6)}
Now A: 'head appears on the coin'
and B: '3 appears on the dice'.
therefore space space straight A space equals space left curly bracket left parenthesis straight H comma 1 right parenthesis comma space left parenthesis straight H comma space 2 right parenthesis comma space left parenthesis straight H comma space 3 right parenthesis comma space left parenthesis straight H comma space 4 right parenthesis comma space left parenthesis straight H comma space 5 right parenthesis comma space left parenthesis straight H comma space 6 right parenthesis
and straight B space equals space open curly brackets left parenthesis straight H comma space 3 right parenthesis comma space left parenthesis straight T comma space 3 right parenthesis close curly brackets
Also, straight A space intersection space straight B space equals space left curly bracket left parenthesis straight H comma space 3 right parenthesis right curly bracket
therefore space space space straight P left parenthesis straight A right parenthesis space equals space 6 over 12 space equals 1 half comma space space space space straight P left parenthesis straight B right parenthesis space equals space 2 over 12 space equals space 1 over 6
and straight P left parenthesis straight A space intersection space straight B right parenthesis space equals space 1 over 12.
Now,       straight P left parenthesis straight A right parenthesis space cross times space straight P left parenthesis straight B right parenthesis space equals space 1 half cross times 1 over 6 space equals 1 over 12 space equals space straight P left parenthesis straight A space intersection space straight B right parenthesis.
∴ A and B are independent.

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