4

Set 15: Systems of Equations

Explanation

Answer: C

A catering service charges $200 setup fee plus $25 per person. Another service charges $150 setup and $30 per person. For how many people do both services cost the same?

A.

8 people

B.

12 people

C.

10 people

✓ Correct
D.

15 people

Detailed Explanation

Choice C is correct. Choice C is the correct answer. Let pp be the number of people. Service 1: C1=200+25pC_1 = 200 + 25 p Service 2: C2=150+30pC_2 = 150 + 30 p Set equal: $$$200+ 25 p = 150 + 30 p200150=30p25p200- 150 = 30 p - 25 p50= 5 pp = 10$$ Solution: 10 people Verification: - Service 1: $$200+ 25(10) = 450$$ - Service 2: $$150+ 30(10) = 450$$ ✓ Strategic Tip: Break-even analysis finds where two linear models intersect. Choice A is incorrect because at 8: Service 1 = 400, Service 2 = 390.ChoiceBisincorrectbecauseat12:Service1=390. Choice B is incorrect because at 12: Service 1 = 500, Service 2 = 510.ChoiceDisincorrectbecauseat15:Service1=510. Choice D is incorrect because at 15: Service 1 = 575, Service 2 = $600.

Key Steps:

The correct answer is 10 people

Why others are wrong:
A: Choice A is incorrect and may result from a calculation error.
B: Choice B is incorrect and may result from a calculation error.
D: Choice D is incorrect and may result from a calculation error.

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