2010 AMC 12B Problem 8

Below is the professionally curated solution for Problem 8 of the 2010 AMC 12B, from LIVE by Po-Shen Loh. You can also try the full timed exam, view all 2010 AMC 12B solutions, or check the answer key.

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Concepts:median (data)parityinequality

Difficulty rating: 1490

8.

Every high school in the city of Euclid sent a team of 33 students to a math contest. Each participant in the contest received a different score. Andrea's score was the median among all students, and hers was the highest score on her team. Andrea's teammates Beth and Carla placed 3737th and 6464th, respectively. How many schools are in the city?

2222

2323

2424

2525

2626

Solution:

With nn schools there are 3n3n students. Carla placed 6464th, so 3n643n\ge64 and n22.n\ge22.

The scores are distinct and Andrea is the median, so 3n3n is odd, forcing nn odd and n23.n\ge23.

Andrea's position is 3n+12,\dfrac{3n+1}{2}, and she beat Beth (3737th), so 3n+12<37,\dfrac{3n+1}{2}\lt37, giving 3n<733n\lt73 and n24.n\le24. The only odd value is n=23.n=23.

Thus, the correct answer is B.

Problem 8 in Other Years