1985 AMC 8 Problem 23

Below is the professionally curated solution for Problem 23 of the 1985 AMC 8, from LIVE by Po-Shen Loh. You can also try the full timed exam, view all 1985 AMC 8 solutions, or check the answer key.

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Concepts:double counting

Difficulty rating: 950

23.

King Middle School has $1200$ students. Each student takes $5$ classes a day. Each teacher teaches $4$ classes. Each class has $30$ students and $1$ teacher. How many teachers are there at King Middle School?

$30$

$32$

$40$

$45$

$50$

Solution:

Each day there are $1200 \times 5 = 6000$ student-class attendances. Since each class holds $30$ students, there are $\dfrac{6000}{30} = 200$ classes.

Each teacher teaches $4$ classes, so there are $\dfrac{200}{4} = 50$ teachers.

Thus, the correct answer is E .

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