AMC8 2018

AMC8 2018 · Q8

AMC8 2018 · Q8. It mainly tests Averages (mean).

Mr. Garcia asked the members of his health class how many days last week they exercised for at least 30 minutes. The results are summarized in the following bar graph, where the heights of the bars represent the number of students. What was the mean number of days of exercise last week, rounded to the nearest hundredth, reported by the students in Mr. Garcia's class?

Garcia先生询问他的健康课成员上周锻炼至少30分钟的天数。结果总结在下面的条形图中，条的高度表示学生人数。学生们报告的上周锻炼天数的平均数，四舍五入到最近的百分位，是多少？

(A) 3.50 3.50

(B) 3.57 3.57

(D) 4.50 4.50

(E) 5.00 5.00

Answer

Correct choice: (C)

正确答案：（C）

Solution

Answer (C): The number of students surveyed was $1+3+2+6+8+3+2=25$, and the number of days of exercise reported was $1\cdot1+3\cdot2+2\cdot3+6\cdot4+8\cdot5+3\cdot6+2\cdot7=109$. So the mean number of days of exercise was $109\div25=4.36$.

答案（C）：被调查的学生人数为 $1+3+2+6+8+3+2=25$，报告的运动天数总和为 $1\cdot1+3\cdot2+2\cdot3+6\cdot4+8\cdot5+3\cdot6+2\cdot7=109$。因此，平均每人运动的天数为 $109\div25=4.36$。

Topics

AR.006 Averages (mean)