2005 AMC 8 Problem 14

Below is the professionally curated solution for Problem 14 of the 2005 AMC 8, from LIVE by Po-Shen Loh. You can also try the full timed exam, view all 2005 AMC 8 solutions, or check the answer key.

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Concepts:double countingbasic counting

Difficulty rating: 1220

14.

The Little Twelve Basketball Conference has two divisions, with six teams in each division. Each team plays each of the other teams in its own division twice and every team in the other division once. How many conference games are scheduled?

8080

9696

100100

108108

192192

Solution:

Let us focus on one team. This team plays against 55 other teams twice in its own division, for a total of 25=102 \cdot 5 = 10 games.

This team also plays 66 games with teams from the other division. Therefore, they play a total of 10+6=1610 + 6 = 16 games.

There are 1212 teams total, so there are 1216=19212 \cdot 16 = 192 games conducted. Each game, however, involves 22 teams, so we have to divide by 2.2.

This gives us the actual total number of games to be 192÷2=96.192 \div 2 = 96.

Thus, B is the correct answer.

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