求教几道，prep数学题，一点儿思路都没有。谢谢

francislaw

a certain city with a population of 132,000 is to be divided into 11 voting districts, and no district is to have a population that is more than 10 percent greater than the population of any other district. What is the minimum possible population that the least populated district could have?



the table shows the number of shared of each of the 5 stocks owned by Mr Sami．　If Mr Sami was to sell 20 shares of Stock X and buy 24 shares of Stock Y, what could be the increase in the range of the numbers of shares of the 5 stocks owned by Mr Sami?


Stock   number of shares
V  68
W 112
X  56
Y 94
Z 45





Henry purchased 3 items during a sale. He received a 20 percent discount off the regular price of the most expensive item and a 10 percent discount off the regular price of each of the other 2 items. was the total regular price of the 3 discounts greater than 15 percent of the sume of the regular prices of the 3 items?
（1） the regular price of the most expensive itme was $50, and the regular price of the next most expensive item was $20.
(2) the regular price of the least expensive item was $15.



If the terms of a sequence are t1,t2,t3,……， what is the value of n?
(1) The sume of the n terms is 3,124.
(2) The average (arithmetic mean) of the N terms is 4.

谢谢，各位大牛。

DMelody

Henry purchased 3 items during a sale. He received a 20 percent discount off the regular price of the most expensive item and a 10 percent discount off the regular price of each of the other 2 items. was the total regular price of the 3 discounts greater than 15 percent of the sume of the regular prices of the 3 items?
（1） the regular price of the most expensive itme was $50, and the regular price of the next most expensive item was $20.
(2) the regular price of the least expensive item was $15.


这一道还是不是很懂阿 求解释啊

hexiaoyulee

楼上写错了，不好意思，没注意看已经解决了

hexiaoyulee

Stock     Number of shares
V               68
W             112
X               56
Y               94
Z                45

The table shows the number of shared of each of the 5 stocks owned by Mr Sami．　If Mr Sami was to sell 20 shares of Stock X and buy 24 shares of Stock Y, what could be the increase in the range of the numbers of shares of the 5 stocks owned by Mr Sami?

-------------------------------------------------------
卖之前的range是w-z=112-45=67

francislaw

谢谢，ALGT的分析，果然犀利，直接道破啊

ALGT

不要看我说简单的那个方法，那无非是利用了这个题的一点特殊性，没意思的。

这个题的表格是整理了两个数字之和。目标是求出m和n的值，那就看m和n出现的位置和涉及的加法等式，如果其中仍有未知量，那就对该未知量在别处的加法等式中算出值，然后回头就知道m和n的值了

-- by 会员 ALGT (2011/7/4 0:46:49)

所谓那个简单一点的，其实是对这个表格更深一点点的理解，没啥用，还是顺便说一下：
既然表格是两数字做和，那有个规律就是：
同一行的两个数字，是两个数字（最顶上那一行中的两个）加上同一个数字（该行最左边的数字）得出的结果，那么
另一行的对应列两个数字，是这两个数字加上另一个数字得出的结果
每行两个结果相减，就把“加上同一个数字”的效果去除而等于原始顶行两个数字的差，而和该行左边，开始加的那个数字无关


两组都是，自然可以列等式。。。

ALGT

What it the greatest common divisor of positive integers m and n？

（1） m is a prime number
(2)  2n = 7m

++++++++
思路是否是：1）和2）联合，m只能等于2 了，也就是最大公约数是1了？
谢谢。

In the xy-plane, at what two points does the graph of y = (x+a)(x+b) intersect the x-axis?
1） a + b= -1
2) The graph intersects the y-axis at (0,-6)

求思路。谢谢。

-- by 会员 francislaw (2011/7/3 19:53:51)

第一题你说的对
第二题，抛物线和x轴交点为（－a，0），（－b，0），因此该题目就是求a，b的值
两个条件分别是
1）a+b=1
2) ab=-6
1）+2）可知a和b一个是3，一个是－2，但是谁是a谁是b无所谓，因为反正求交点，两个交点已经出来了

ALGT

不要看我说简单的那个方法，那无非是利用了这个题的一点特殊性，没意思的。

这个题的表格是整理了两个数字之和。目标是求出m和n的值，那就看m和n出现的位置和涉及的加法等式，如果其中仍有未知量，那就对该未知量在别处的加法等式中算出值，然后回头就知道m和n的值了

francislaw

What it the greatest common divisor of positive integers m and n？

（1） m is a prime number
(2)  2n = 7m

++++++++
思路是否是：1）和2）联合，m只能等于2 了，也就是最大公约数是1了？
谢谢。

In the xy-plane, at what two points does the graph of y = (x+a)(x+b) intersect the x-axis?
1） a + b= -1
2) The graph intersects the y-axis at (0,-6)

求思路。谢谢。

francislaw

+  X  Y  Z
4  1  -5 m
e  7  n  10
f  2  -4  5

In the addition table shown above, what is the value of m + n?

选项
-19，4 ，5，6，22

这个题的重点也是看懂题：
4 + x ＝ 1, x = -3
4 + y = -5, y = -9
e + x = 7, e = 10
e + y = n, n = 1
e + z = 10, z = 0
4 + z = m, m = 4


m + n = 5


或者有个简单方法：
可以直接看出来： m - (-5) = 10 - n
直接得出m+n=5～

-- by 会员 ALGT (2011/7/3 10:55:18)

谢谢ALGT
这个题是从哪儿入手呢？