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There are 8 chocolates in a box - HSC - SSCE Mathematics Standard - Question 11 - 2021 - Paper 1

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There are 8 chocolates in a box. Three have peppermint centres (P) and five have caramel centres (C). Kim randomly chooses a chocolate from the box and eats it. Sam... show full transcript

Worked Solution & Example Answer:There are 8 chocolates in a box - HSC - SSCE Mathematics Standard - Question 11 - 2021 - Paper 1

Step 1

Kim chooses P, Sam chooses C

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Answer

The probability that Kim chooses a peppermint chocolate is ( P(K = P) = \frac{3}{8} ). After Kim has taken a peppermint chocolate, there are now 7 chocolates left, with 5 being caramel. Thus, the probability that Sam chooses a caramel chocolate is ( P(S = C | K = P) = \frac{5}{7} ). Therefore, the combined probability is:

P(K=P,S=C)=P(K=P)×P(S=CK=P)=38×57=1556. P(K = P, S = C) = P(K = P) \times P(S = C | K = P) = \frac{3}{8} \times \frac{5}{7} = \frac{15}{56}.

Step 2

Kim chooses C, Sam chooses P

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Answer

The probability that Kim chooses a caramel chocolate is ( P(K = C) = \frac{5}{8} ). If Kim has taken a caramel chocolate, there are now 7 chocolates left: 3 being peppermint. Thus, the probability that Sam chooses a peppermint chocolate is ( P(S = P | K = C) = \frac{3}{7} ). Therefore, the combined probability is:

P(K=C,S=P)=P(K=C)×P(S=PK=C)=58×37=1556. P(K = C, S = P) = P(K = C) \times P(S = P | K = C) = \frac{5}{8} \times \frac{3}{7} = \frac{15}{56}.

Step 3

Total probability of different centres

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Answer

The total probability that Kim and Sam choose chocolates with different centres is the sum of the two probabilities computed:

P(different)=P(K=P,S=C)+P(K=C,S=P)=1556+1556=3056=1528. P(different) = P(K = P, S = C) + P(K = C, S = P) = \frac{15}{56} + \frac{15}{56} = \frac{30}{56} = \frac{15}{28}.

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