2012 AMC 8 Problem 22

Below is the video solution and professionally curated solution for Problem 22 of the 2012 AMC 8, from LIVE by Po-Shen Loh. You can also try the full timed exam, view all 2012 AMC 8 solutions, or check the answer key.

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Concepts:median (data)casework

Difficulty rating: 1720

22.

Let RR be a set of nine distinct integers. Six of the elements are 2,2, 3,3, 4,4, 6,6, 9,9, and 14.14. What is the number of possible values of the median of R?R?

4 4

5 5

6 6

7 7

8 8

Video solution:
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Written solution:

In a sorted set of nine distinct integers, the median is the fifth number.

The median cannot be below 33, since then 3,4,6,9,143,4,6,9,14 would already give at least five larger elements. It cannot be above 99, since 2,3,4,6,92,3,4,6,9 would already give at least five smaller elements.

Each integer from 33 through 99 can be made the median by choosing the three missing integers appropriately. Therefore there are 77 possible medians. Thus, the answer is D .

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