1.Amy's grade was the 90th percentile of the 80 grades for her class. Of the 100 grades from another class, 19 were higher than Amy's, and the rest were lower. If no other grade was the same as Amy's grade, then Amy's grade was what percentile of the grades of the two classes combined?
(A) 72nd
(B) 80th
(C) 81st
(D) 85th
(E) 92nd
请详细讲一下 percentile 这个词的理解，谢谢！
2.An automobile manufacturer offers a station wagon with either a 6-cylinder engine or a 4-cylinder engine and with either a manual transmission or an automatic transmission. A trailer hitch is also offered, but only on a station wagon with a 6-cylinder engine. How many combinations of the five options listed does the manufacturer offer for its station wagon?
(A) 3
(B) 4
(C) 5
(D) 6
(E) 8
请您更正或指点我的理解，谢谢！ 我的理解是：题意中是不是隐含着6-cylinder engine 可以不带 trailer hitch? 如果是的话，本题中有三个分类：（1）station wagon with either a 6-cylinder engine or a 4-cylinder engine （2） with either a manual transmission or an automatic transmission （3）就是带 trailer hitch 的6-cylinder 车和不带 trailer hitch 的6-cylinder 车
3.
70, 75, 80, 85, 90, 105, 105, 130, 130, 130
The list shown consists of the times, in seconds, that it took each of 10 schoolchildren to run a distance of 400 meters. If the standard deviation of the 10 running times is 22.4 seconds, rounded to the nearest tenth of a second, how many of the 10 running times are more than 1 standard deviation below the mean of the 10 running times?
(A) One
(B) Two
(C) Three
(D) Four
(E) Five
请帮忙详细讲解一下 rounded to the nearest tenth of a second 这句话。我的疑问是这句话到底是理解为：精确到十分之一秒即小数点后一位还是理解为：将最近的十分之一秒调整为整数，即按照四舍五入的原则，此处约等于22 seconds？
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