求助数学题····

saiko13

1. each of 20 parents chose one of five days from Monday through Friday to attend parent-teacher conference. If more parents choose Monday than Tuesday, did at least one of the parents choose Friday?
(1) None of the five days was chosen by more than 5 parents.
(2) More parents chose Monday than Wednesday.
A  

2. A cash register in a certain clothing store is the same distance from two dressing rooms in the stores. If the distance between the two dressing rooms is 16 feet. which of the following could be the distance between the cash register and either dressing room.
(1) 6 feet
(2) 12 feet
(3)24 feet
A (1) only
B (2) only
C (3) only
D (1) and (2)
E (2) and (3)

E


3. The posiytive numbers w,x,and y,z are such that. x is 20% greater than y, y  is 20% greater than z, and w is 20% less than x. what percent greater than z is w?
A 15.2%
B 16.0%
C 20.0%
D 23.2%
E 24.8%

A
这道题的式子是不是这样列的？x-20%x=y   y-20%y=z  w+20%w=x?

4. if the units digit of the three-digit positive integer k is nonzero, what is the tens digit of k? A
(1) the tens digit of k+9 is 3
(2) the tens digit of k+4 is 2



感谢各位大侠走过路过，帮忙看看···

另外两道：
5。for any number x,|x| denotes the greatest integer less than or equal to x, what is the value of |-10\4|?
A 0
B -1
C -2
D -3
E -4

D  这道题我怎么就算不出来等于-3？

6。for a certain car repair, the total charge consisted of a charge for parts, a charge for labor, and a 6% sales tax on both the charge for parts and the charge for labor. if the charge for parts, excluding sales tax, was $50.00. what was the total charge for the repair?
(1) the sales tax on the charge for labor was $9.6
(2) the total sales tax was $12.6

D  不明白为什么第一个可以算出来？

子夜风衍

第1题
A 因为20人 如果没有周五 只有4天
A说一天最多5人 题目说周一和周四不一样 因此剩余四天全5人不成立 （周一和周四数不一样）所以得出结论周五必定有人去

子夜风衍

第二题

两边之和大于第三边

子夜风衍

第三题

x=1.2y
y=1.3z
w=0.8x

so w=1.152z

子夜风衍

第四题

条件2有两个结果
2和1

条件1 只能是2

maximeason

同意 第四个我没看懂第二个为什么不行

saiko13

非常感谢大侠的帮助······

saiko13

可不可以这样理解：
（1）K+9  K是非零的 那么加上一个数 是肯定进一位  所以只有一种情况
（2）K+4 就不一定了 有可能进一位 也有可能保持原来 所以有两种情况

ZKRAP

第四题 举例吧 最笨但是最实用的方法
K+9 十位数是三 假设100<k<200 则K只能取121-129 （个位非零）所以推出十位是2

K+4 十位数是二 假设100<k<200 则K可取118 121都行 ，但是十位数就不确定了