AnswersGrade 7 MathematicsPractice ExamQuestion 22
22
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Practice Exam

Question 22 • Grade 7 Mathematics

Kiesha’s quality-control manager told her she must have 97 percent of her clocks functioning properly. She found a report that said 6 out of 300 clocks tested were not working properly. Kiesha predicts that she will have enough working clocks to please the manager. Which statements are true about Kiesha’s prediction? Choose three correct answers.

Answer
A
Kiesha’s experimental probability is 1 over 30 .
B
When the inventory is 4000 clocks, the prediction is that 3920 clocks will work.
C
Kiesha will not meet 97 percent because more than 3 percent of her clocks will be broken.
D
Kiesha’s experimental probability is 1 over 50 .
E
Kiesha will have more than 97 percent of the products working.

Explanation

The experimental probability that a clock is not working is 6/300 = 1/50, so D is true. That means about 49/50, or 98%, of the clocks are expected to work, which is more than the required 97%, so E is true. For 4,000 clocks, 98% × 4,000 = 3,920 working clocks, so B is true.

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