MOST of the math on the SAT (Scholastic Aptitude Test,美国高考)

MOST of the math on the SAT (Scholastic Aptitude Test,美国高考) is from subjects Chinese students studied long before high school.But although it is simple,many Chinese students struggle to reach their potential (潜力) on the math test.Students rarely struggle with equations (方程式) and functions (函数).However,when they need to break down a long word problem,they are more likely to make mistakes.Take a look at this problem.
A store sells all maps at one price and all books at another price.On Monday,the store sold 12 maps and 10 books for a total of $38,and on Tuesday the store sold 20 maps and 15 books for a total of $60.At this store,how much less does a map sell for than a book?
(A) $.25 (B) $.50
(C) $.75 (D) $1.50
(E) $2.00
I am sure some of you correctly chose B as the right answer,but many of you will have made a mistake somewhere along the line.The first trick in this question is finding a way to compare the total sales from both days.We’ve learned that 12 maps and 10 books earn $38 one day,and 20 maps and 15 books earn $60 the other day.Therefore,we know that 2 maps cost $3 and a single map costs $1.50.This means that books cost $2 and that the difference is 50 cents.
The difficulty most students face is in the final part of the question.The answer you need to give is the difference in price between the two.This is a common trick the test writers use to get students to answer the wrong questions.If any of you picked D or E,you probably did the math correctly,but simply answered a different question than the one that was asked.Cutting down on these mistakes is often the difference between a perfect score and a score that is just a little above average.
我还是搞不懂,为什么不是0.5

重点看这些：
我相信有些学生会选B为正确答案,而大多数学生也会出现某些方面错误.解题的第一个技巧是找到一种方法去对比两天的总数.我们会得出一天12张地图10本书赚38美元,而另一天20张地图15本书赚60美元.因此,我们算出2张地图要3美元,那么1张地图1.5美元.这就意味着书是2美元,地图与书的差是0.5美元.
绝大多数学生面对的困难是问题的最后一部分,你要给出的答案是两样东西的价格差.这是出题人常用的技巧让学生得出错误的答案.如果有人选了D和E答案的话,你或许选对了,但是只不过是回答了不同问题而不是要问的问题.减少这类错误就是满分和比普通分略高一点儿的差异之处了.