SOLUTION: Twin sisters, Sue and Debbie, are both good math students. their mathematics teacher calculated that sue has a probability of 0.7 of getting an A at the end of the year and Debbie

Question 449711: Twin sisters, Sue and Debbie, are both good math students. their mathematics teacher calculated that sue has a probability of 0.7 of getting an A at the end of the year and Debbie has a probability of 0.6. Find the probability that:
i) Neither gets an A.
ii) if only one gets an A , its is Sue.
Answer by stanbon(75887) (Show Source): You can put this solution on YOUR website!
Twin sisters, Sue and Debbie, are both good math students. their mathematics teacher calculated that sue has a probability of 0.7 of getting an A at the end of the year and Debbie has a probability of 0.6. Find the probability that:
i) P(Neither gets an A) = (1-0.7)(1-0.6) = 0.3*0.4 = 0.12
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ii) if only one gets an A , it is Sue.
P(both get an A) = 0.7*0.6 = 0.42
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P(one gets an A) = = 0.7+0.6-0.42 = 1.3-0.42 = 0.88
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P(only one gets A) = 1-[0.12+0.42] = 1-0.54 = 0.46
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P(Sue gets A | one gets A) = P(one gets A AND Sue gets A)/P(one gets A)
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= P(Sue gets A)/P(one gets A) = 0.7/0.88 = 0.7955
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Cheers,
Stan H.

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