希望跟大家讨论几道数学题

ethan_wongUID: 2172215

1.For how many positive three-digit numbers is the average of the three digits equal to 2?
   此题答案是21。不解。请各位帮忙告诉我是哪21个数。
( a! a! ^8 g/ X8 O! d$ _/ J2.If (x+y)(x-y)+(4-y)(2-y)=0,then what is the value of y when x equals 8?
, }0 X9 y0 V+ [, E- R: F5 a( d   此题答案是-9.3333333，是否是答案错了
3.If 3/5 of 1/3 is divided into 4,what is the resulting value?
! E: X- h$ o( B) k  l$ ?1 i8 k   此题题目是什么意思？请强人翻译
4.If (2+a)(b-2)=0,which of the following could be true?
0 H5 T' t# X; h2 [   I.a=-2   II.b=2   III.a=-b
, {/ `! x) P+ A3 O4 E+ o   此题答案是I,II,III
   请问如何理解III?
) w$ [& P; s, t' Y5.A certain clock has a minute hand that is exactly twice as long as its hour hand.If point A is at the tip of the minute hand,and point B is at the tip of the hour hand,what is the ratio of the distance that point A travels in 3 hours to the distance that point B travels in 9 hours?
  p' H0 I! o* B$ f8 {- E3 t+ N/ {   此题答案是2：3，请大家说说是不是这个数？请解释
7 v, g; s9 s$ C6.If a set of 2x consecutive numbers has y even numbers and the first number in the set is 1,which of the following must be the largest odd number in the set?
   此题答案是2y,我不明白阿，谁能解释解释？
7.In a list of five integers,if the mode of the list is two less than the median,which of the following could be true?
( Q+ k" b7 \. T0 X  A% h   答案是the average is less than the median.这个statement正确吗？
6 Z; b* Z; c4 @# s; h8.In a sequence of numbers,the first term is 6.Each successive term following the first is calculated by adding 2 to the perivous term and then dividing by -1.what is the value of the 101st term subtracted from the 70th term?
( D1 T, u  l' q: i' S5 E8 o   此题答案是-14，请问是这个结果吗，我不明白，请解释
9.请高人给出矩阵的算法

hyacinthUID: 2184492

1.我还要再想一想,暂时不明白题目啥意思.
2.我觉得答案好象不对.
: p& ]! N* j. R- m: Y3.不就是3/5×1/3÷4
4.a=-b时,-(b-2)的平方为0,而平方数一定大于等于0,所以前式一定为0
/ B) D) y" }% m% b5 M) h  S# z/ D- K5.假设分针的长度为2R,那么时针的长度为R.3小时后,分针走过的距离为1/4×2π×2R=πR,
时针走过的距离等于3/4×2πR=3/2πR.两个的比自然是2:3
  A  T) @  _/ `" _( n  U6.2x有y个连续偶数,最小的是1,最大的自然是2y
& w8 f" d; ?$ \& M, W+ q& X7.mode是众数,也就是出现频率最高的数字.我觉得这个statement不对.众数貌似属于linear algebra,统计里出现的比较多
8.数列问题.数列的奇数项都是6,偶数项都是-8.所以答案为-8-6=-14
! ]9 \( t  \4 l7 X7 _9 N! A5 N矩阵也考啊?这明显属于linear algebra了.建议LZ自己找书去看,如果SAT的数学涉及到这部分的话.(我自己也没学过,也要补了)

hyacinthUID: 2184492

总算搞明白了600,510,501,105,150,420,402,204,240,321,312,231,213,123,132,222,411,141,114,303,330
2 G9 z3 C. D; }. ^: P第二题,y应该是12吧

ethan_wongUID: 2172215

太精彩了，谢谢你

ethan_wongUID: 2172215

If set A consists of all prime numbers less than 30,and set B consists of all positive mutiples of 3 less than 30,how many elements are there in A并B?
此题答案是18，我感觉有19个阿

ethan_wongUID: 2172215

第五题分针走过的距离为什么是πR？？分针不是转了3圈吗？

hyacinthUID: 2184492

你3算重了吧.
9 o4 y8 Y4 J7 M* J6 F$ j+ h6 K! ?" j没什么好谢的啦,我反正也准备考SAT,就当是熟悉题目了,说到这,我还要感谢你提供题目让我练习呢~
0 `' ^9 P2 v% ^) L% R" h4 D你这是SAT1or2?

ethan_wongUID: 2172215

SAT1,june3.

hyacinthUID: 2184492

NO.5.是我错了
我跟同学讨论了下.答案不对

zcy870611UID: 2196648

答案应该是8:1吧？
5 w# N+ a: f' t' a9 `0 b- |分针转三圈是３＊２＊２派R=12派R
时针转３／４圈是３／４＊２派R= 3/2派R
我也不清楚哦，有定论了讲一下啊
楼主要多发题目啊～～语法和阅读有吗？

sk8er_kittenUID: 2210858

第一题,应该是105 501 150 510 114 141 411 123 132 321 213 231 312 222 600 240 420 204 402 303 330