求助！！！感激不尽泪流满面了！！

yexianda · 发表于 2013-1-12 21:06:39

What is the average of eleven consecutive integers?
1.   The average of the first nine integer is 7
2.   The average of the last nine integers is 9
D
For which of the following functions is f(a+b)=f(a)+f(b) for all positive numbers a and b?
a.   f(x)=x2 b. f(x)=x+1 c. f(x)=根号x d. f(x)=2/x e. f(x)=-3x

According to the directions on a can of frozen orange 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?
25

If n is a positive integer and the product of all the integers from 1 to n, inclusive, is a multiple of 990, what is the least possible value of n?
Answer:11

If M is a finite set of negative integers, is the total number of integers in M an odd number?
a.   The product of all the integers in M is odd b. The product of all the integers in M is negative
b.   B

In a stack of boards at a lumber yard, the 20th board counting from the top of the stack is immediately below the 16th board counting from the bottom of the stack. How many boards are in the stack?
34

In the finite sequence of positive integers k1,k2,k3….k9 each term after the second is the sum of the two terms immediately preceding it. If k5=18, what is the value of K9?
a.   k4=11
b.   k6=29
c.   D

For a finite sequence of nonzero numbers, the number of variations in sign is defined as the number of pairs of consecutive terms of the sequence for which the product of the two consecutive terms is negative. What is the number of variations in sign for the sequence 1,-3,2,5,-4,-6?
3

If x and y are positive integers, what is the value of xy?
The greatest common factor of x and y is 10
The least common multiple of x and y is 180
C
For each month of next year, Company R’s montly revenue target is X dollars greater than its monthly revenue target for the preceding month. What is Company R’s revenue target for March of next year?
Company R’s revenue target for December of next year is 310,000
Company R’s revenue target for September of next year is 30,000 greater than its revenue target for June of next year
C

For all positive integers m, m=3m when m is odd and m=1/2m when m is even. Which of the following is equivalent to 9x5?
27

At a two-day seminar. 90 percent of those registered attended the seminar on the 1st day, what percent of those registered did not attend the seminar on either day?
A total of 1,000 people registered for the 2-day seminar
Of those registered, 80 percent attended the seminar on the second day
E

What is the sum of the different positive prime factors of 550?
15
本人数学基础很差。。。实在不好意思了。。。麻烦大侠们同学们战友们了。。。谢谢~~~

yinghua9122 · 发表于 2013-11-9 21:55:31

What is the average of eleven consecutive integers?
1. The average of the first nine integer is 7
2. The average of the last nine integers is 9
D

前9个连续数的均值就是这个数列第5个数的值，因为9是奇数，这个数列前四个，中间一个，后面四个，是对称的。又因为是连续数，所以平均数不就是中间那个数吗？
比如：1,2,3,4,5,6,7,8,9 5是中间数，自然就是这个连续数列的均值了，对吧？
同理，11个连续数的均值不就是第6个数吗？

第一个条件说前九个数的均值是7，那么这个数列第五个数是7，那第六个数不就是8喽。这第六个数不就是11个数的均值喽。

yinghua9122 · 发表于 2013-11-9 22:07:44

For which of the following functions is f(a+b)=f(a)+f(b) for all positive numbers a and b?
a. f(x)=x2
b. f(x)=x+1
c. f(x)=根号x
d. f(x)=2/x
e. f(x)=-3x
把a+b ，a, b 分别带入到函数中，看看成不成立
如果没看错，a是说平方吧。左边x=a+b, 则f(x) =（a+b）^2 = a^2 +2ab+ b^2 , 这是平方和公式，很显然不等于f(a)+f(b)=^2 + B^2
b选项，f(x)=x+1，则F（a+b）= a + b +1, 而 f(a)+f(b) = a +1 + b +1, 不成立吧。
后面的，你自己一个一个试就行。

yinghua9122 · 发表于 2013-11-9 22:19:25

According to the directions on a can of frozen orange 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?
25

首先你需要看懂题目，题目的意思是：1罐浓缩的orange 要兑 3罐的水来让它变成orange juice。所以会和比例1:3 ，但是需要注意在concentrate orange :orange juice = 1:4,因为你把它混合起来了， 1+3 =4

现在需要200个每个罐6盎司的orange juice，所以总共的orange juice是200*6 = 1200盎司，所以根据比例可知道浓缩的orange 需要300盎司

而浓缩的 orange 是每罐12盎司罐装的，所以需要这样的罐子 300/ 12 = 25

明白否？

求助！！！感激不尽泪流满面了！！

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