《最新GMAT数学机考模拟150题》陈向东中三题不会 请指教谢谢

1. The people eating in a certain cafeteria are
either faculty members or students, and the number of faculty members is 15 percent
of the total number of people in the cafeteria. After some of the students
leave, the total number of persons remaining in the cafeteria is 50 percent of
the original total. The number of students who left is what fractional part of
the original number of students?

A.17/20    
B.10/17       C.1/2       D.1/4      E.7/20

正确答案是：B       我做的是C，请帮忙告诉我怎么做的？

2. The enrollments at College X and College Y both
grew by 8 percent from 1980 to 1985. If the enrollment at College X grew by 800
and the enrollment at College Y grew by 840, the enrollment at College Y was
how much greater than the enrollment at College X in 1985?

A.400         
B.460        C.500       D.540       E.580
正确答案：D     我做的是C，请帮忙告诉我怎么做的？

3. A figure that can be folded over along a
straight line so that the result is two equal halves which are then lying on
top of one another with no overlap is said to have a line of symmetry. Which of
the following figures has only one line of symmetry?

A. square     
B. circle        C. equilateral
triangle      D. isosceles triangle

E. rectangle

正确答案是：D

题目没看懂，请帮忙翻译一下……谢谢了啊……

1.if x is the oringinal total, 走的学生就是50%x，原来学生是85%x，这样，50%x/85%x=10/17

2.(840/8%)+840-(800/8%+800)=540

3.一个图形沿一条直线对折后的结果是对折后的两部分相等,即完全没有重叠的一部分在另一部分之上,就说它们有一条对称线, 下面哪一个图形只有一条对称线?(差不多就是这个意思)

如果有不对之处还请大家谅解.

up

我也想要，能否给我也发一个？

hotcandle(＠) 126.C0M

谢谢~感激不尽！