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CBSE Class 12 Math 2012 Solved Paper
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Question : 28 of 29
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A girl throws a die. If she get a 5 OR 6, she tosses a coin three times and notes the number of heads. If she gets 1, 2, 3 OR 4, she tosses a coin two times and notes the number of heads obtained. If she obtained exactly two heads, what is the probability that she threw 1, 2, 3 OR 4 with the die?
Solution:
Consider the following events: = Getting 5 OR 6 in a single throw of the die = Getting 1, 2, 3 OR 4 in a single throw of the die A = Getting exactly 2 heads We have to find, P(/A). Since P (/A) =
Now, = = and = = Also, P (A|) = Probability of getting exactly 2 heads when a coin is tossed 3 times = And, P (A|) = Probability of getting 2 heads when a coin is tossed 2 times = ∴ P (|A) = = = =
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