AnswersGrade 7 MathematicsProbability of Compound Events — QuizQuestion 1
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QuizMultiple Choice

Probability of Compound Events — Quiz

Question 1 • Grade 7 Mathematics

Xander spends most of his time with his 10 closest friends. He has known 4 of his 10 friends since kindergarten. If he is going to see a movie tonight with 3 of his 10 closest friends, what is the probability that the first 2 of the friends to show up to the movie are friends he has known since kindergarten but the third is not?

Answer
A
1 over 30
B
12 over 125
C
9 over 125
D
1 tenth

Explanation

The first friend has a 4/10 chance of being someone Xander has known since kindergarten. After that, 3 of the 9 remaining friends are kindergarten friends, and then 6 of the 8 remaining are not. Multiply: (4/10) × (3/9) × (6/8) = 1/10, so the probability is one tenth (choice D).

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