To model the situation of Heidi's older sister choosing a subject (Physics, Spanish, or Chemistry) and then selecting a period (1 through 6) using a tree diagram, we indeed have different ways to structure the tree.
Analysis of Options:
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Option A suggests that you can structure the tree diagram in two ways (subjects at the top or periods at the top) and that they provide different outcomes. This is somewhat misleading; while you can structure it in two ways, both will ultimately lead to the same number of outcomes, as the relationships between the choices do not change.
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Option B correctly states that both ways provide the same number of outcomes. Specifically:
- If subjects (P, S, C) are on the top level, each subject has 6 branches (for periods), leading to a total of \(3 \times 6 = 18\) outcomes.
- Conversely, if periods (1 through 6) are on the top level, each period has 3 branches (for subjects), also leading to \(6 \times 3 = 18\) outcomes.
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Option C suggests that there is only one correct way to draw the tree diagram, which is not accurate because there are indeed multiple correct ways to draw it, and both yield the same outcome count.
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Option D incorrectly states that a tree diagram cannot be used to model the situation at all, which is not the case.
Conclusion:
Given this analysis, the correct choice is B:
B. Yes. You can make a tree diagram with each subject at the top and the periods as the branches or with the periods at the top and each subject as a branch. Both ways provide the same number of outcomes, 18.