AMC8 2011

AMC8 2011 · Q11

AMC8 2011 · Q11. It mainly tests Averages (mean), Arithmetic misc.

The graph below shows the number of minutes studied by both Asha (black bar) and Sasha (grey bar) in one week. On the average, how many more minutes per day did Sasha study than Asha?

下图显示了Asha（黑条）和Sasha（灰条）在一周内每天学习的时间（分钟数）。平均每天Sasha比Asha多学习了多少分钟？

(A) 6 6

(B) 8 8

(D) 10 10

(E) 12 12

Answer

Correct choice: (A)

正确答案：（A）

Solution

Average the differences between each day. We get $10, -10,\text{ } 20,\text{ } 30,-20$. We find the average of this list to get $\boxed{\textbf{(A)}\ 6}$. ( In case you were wondering, the way to calculate the average is $\frac{(10+(-10)+20+30+(-20))}{5} = \frac{ 30}{5} = 6$. So the answer is indeed $\boxed{\textbf{(A)}\ 6}$)

计算每天差异的平均值。我们得到$10, -10,\text{ } 20,\text{ } 30,-20$。求这个列表的平均值为$\boxed{\textbf{(A)}\ 6}$。（如果你好奇的话，计算平均值的方法是$\frac{(10+(-10)+20+30+(-20))}{5} = \frac{ 30}{5} = 6$。所以答案确实是$\boxed{\textbf{(A)}\ 6}$）

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