没有找到以前的讨论~~~求助几道PREP的数学题~~~~谢谢了

我是橙橙

What is the greatest possible area of a triangular region with one vertex at the center of a circle of radius 1 and the other two vertices on the circle?

(A)3^/4

(B)1/2

(C)pai/4

(D) 1

(E) 2^

答案选B 什么情况下这个三角形的面积是最大的啊

A certain car averages 25 miles per gallon of gasoline when driven in the city and 40 miles per gallon when driven on the highway.  According to these rates, which of the following is closest to the number of miles per gallon that the car averages when it is driven 10 miles in the city and then 50 miles on the highway?

 

 

(A) 28

(B) 30

(C) 33

(D) 36

(E) 38

答案选D

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According to the directions on a can of frozen orange juice concentrate, 1 can of concentrate is to be mixed with 3 cans of water to make orange juice.  How many 12-ounce cans of the concentrate are required to prepare 200 6-ounce servings of orange juice?

 

(A)  25

(B)  34

(C)  50

(D)  67

(E)  100

答案选A

When a certain tree was first planted, it was 4 feet tall, and the height of the tree increased by a constant amount each year for the next 6 years.  At the end of the 6th year, the tree was   taller than it was at the end of the 4th year.  By how many feet did the height of the tree increase each year?

 

 

(A)3/10

 

(B)2/5

 

(C)1/2

(D)2/3

 

(E)6/5
                            

答案选D 可是这不就是个等差数列的题吗？设等差为D 则5D-3D=1/5 得D=1/10啊！

[此贴子已经被作者于2008-4-7 22:32:13编辑过]

我是橙橙

急求解！！各位XDJM帮帮偶哦

dianecarton

第一题，以圆心为顶点，两条半径构成直角的那个三角形面积最大

第二题 25/10 + 40/50 求出总加仑数，再用10+50去除这个数，求出每加仑跑多少英里，答案是个近似值，楼主算算吧

第三题 一份浓缩汁三份水，12盎司的浓缩汁就要36盎司的的水，一共12+36=48盎司， 200杯6盎司的果汁就是 200*6=1200盎司 1200/48=25

第四题，楼主应该落掉了the tree was 1/5  taller than it was ...设d是等差数列公差 4+6d=6/5(4+4d)  d=2/3