All of the 300 students at a high school take the same four courses. Three of the courses are taught in 15 classes of 20 students each. The fourth...

4. All of the 300 students at a high school take the same four courses. Three of the courses are taught in 15 classes of 20 students each. The fourth class is taught in 3 classes of 100 students each. Explain how the school's principal could claim that the mean class size is 25 students, while upset parents could claim that the mean class size is 40 students. Which mean is better? Which mean is fairer?