[数学讨论稿1]石越而是其输血 讨论稿1-100（11月19日15:20 更新）

kelly周

dingding

chendan815

感谢版主的无私奉献！

笨蛋加油

谢啦

allenliu1999

支持LZ一下！

sallyc

xiaotupb

rapturewlx

好的

choumichael

1、楼主答案完全正确。没有做的17题答案是17.
2、球截下来的是DOME。不是TOME。可能是狗主笔误。

trackofheart

jj17
等差数列求n
n = (an-a1)/d + 1
a1 = 3^4 = 81
an = 3^5 = 243

(243-81)/9 + 1 = 18 + 1 = 19

谢谢evafang2008指正

-- by 会员 crusaderma (2011/10/28 2:19:25)

要看题目的吧~现在inclusive的话是19个，但是如果没有就要考虑算不算3^4和3^5了吧~不算应该是17个

-- by 会员 大小白love牛奶 (2011/10/28 9:33:03)

同意！

trackofheart

jj4:
三个人的平均身高为170， 问 median是多少
（1）其中一个165
insufficient, 因为剩下两个可以都比165高，media就出现在另外两个里面(165,170,175)，或者一高一低，中数为165，或者165，165，180，median为165,
(2) 其中一个170
sufficient
因为只能出现一高一低或者同样的情况，median只能为 170
这道题

这题跟GWD MATH11 Q20的思路一样

-- by 会员 crusaderma (2011/10/28 0:35:47)

这题跟og里面ps一道题思路也是。。大家以防变体。。可以看下。。
105. Tom,Jane,andSueeachpurchasedanewhouse.The average (arithmetic mean) price of the three houses was $120,000.
What was the median price of the three houses?
(1)    The price of Tom’s house was $110,000.
(2)    The price of Jane’s house was $120,000.


Arithmetic Statistics
Let T, J, and S be the purchase prices for Tom’s, Jane’s, and Sue’s new houses. Given that the average purchase price is 120,000, or T + J + S = (3)(120,000), determine the
median purchase price.
(1)    Given T = 110,000, the median could be 120,000 (if J = 120,000 and S = 130,000) or 125,000 (if J = 125,000 and S = 125,000); NOT suðcient.
(2)    Given J = 120,000, the following two cases include every possibility consistent with T + J + S = (3)(120,000), or T + S = (2)(120,000).
(i) T = S = 120,000 (ii) One of T or S is less than 120,000 and
the other is greater than 120,000.
In each case, the median is clearly 120,000; SUFFICIENT.
the correct answer is B; statement 2 alone is suðcient.