Check the confirmed JJ 8-24

cook

116：Q    题目说下面那一个不可能是多边形的对角线个数
A 5  B 6  C 9 D14 E21？
要注意一个单词：polygon 是多边形
=========================
Does anybody know how to calcuate the number of diagonals of polygon? thanks!

112.Q:   8苹果6个好的取4个至少1个坏的概率,

A::55.【确定】
=================
My answer: 1-C6,4/C8,4=11/14 =78.6% . Is that correct?

102、Q:how many square feet of carpeting that will be need to cover the floor that 14 feet long
(1) perimeter 52
(2) the greatest distance of 2*根号 85

A:  D【确定】
====================================
How do you know it is regular shape? E or uncomplete issue.

89.  Q:  如果一个定单的书价低于$15,则运费为$3,如果一个定单的书价高于$15,则运费为书价的20%,问两个定单X和Ｙ的运费总共为多少？
1)Ｘ的书价加Ｙ的书价＝$18.75
2)X的书价和Y的书价都高于$4

A:   A【确定】
=============================
My answer: C for example: (15,3.75) or (16,2.72) will get different answers.

86. Q 8人选2人，A去，B不去的概率。

A: 6/C(8，3)【确定】
================
6/C(8,2)

7。Q:There are 8 books, 6 of them are paperbooks and 2 of them are hardbooks. What is the combination of at least one hardbook?

     A:       40【确认】
     R:     C(2,1)*C(6,3)=40   
========================
I think the question isn't clear? please advise!

5。Q:Is integer n a square of integer?   
1)4n is a square of integer
2)n^3 is a square of integer

    A:   C【确认】
    R:for 1,n maybe 1/4,insufficient;
for 2,n maybe 根号3,so insufficient
1+2,N must be integer,so C
========================
D, since n is integer

Thank!

gwxd

我笨，还是看不懂。Cn，2 减去 n。那个逗号是啥意思？/ 比如说6边形怎么算？

tongxun

N 是指N边形，公式是Cn，2 减去 n。

gwxd

多边形的计算公式是啥？？什么是Cn,2-n??应该是n-2,对吗？？我不明白，请指教

tongxun

112、你的答案正确。
86、我将题目看错了，以前有一题目是选3人。6/C8，2 才是正确答案。你对！

tongxun

cook: because I am not in my home now, so I cannot caculate some questions you asked. I will replay these questions tonight.
Sorry!

cook

first, thank you for advise but you confused that my answer is under the confirmed keys which is published on 全部确认过答案的本周数学 (2002-8-25), I just want to clarify and make sure.

116\ Cn,2 -n 这是对角线的运算公式, N 代表N边形. thanks!

112\ 55 是能取的种类,不是概率.
=========
Not for the question. anyway, we are agreed.

102\ 题目应该说明了是长方形. --Ok

89\ 肯定是C, 因为不管你的书是多少价钱,都需要运费. 16+2.75 与 15+3 是不一样的.
===========
You agree with me.

86\ C6,1/C(8，3)
==========
Can you explain why C(8,3) instead of C(8,2)
7\ 题目肯定不完整! 因为没说取几本书. 记得原题为取两本书.
C2,1 * C6,1 +C2,2
========
Yeah, I think so

5\ D I am sure.
===========
you bet.

tongxun

116\   Cn,2 -n 这是对角线的运算公式, N 代表N边形.
112\   55 是能取的种类,不是概率.
102\   题目应该说明了是长方形.
89\   肯定是C, 因为不管你的书是多少价钱,都需要运费. 16+2.75 与 15+3 是不一样的.
86\    C6,1/C(8，3)
7\    题目肯定不完整! 因为没说取几本书. 记得原题为取两本书.
        C2,1 * C6,1 +C2,2
5\  D  I am sure.