急求！！！！数学疑问

ycenyidol · 发表于 2012-3-9 19:50:57

以下是prep数学：
96. According to the directions on a can of frozen orange juice concentrate, 1 can of concentrate is to be mixed with 3 cans of water to make orange juice.How many 12-ounce cans of the concentrate are required to prepare 200 6-ounce servings of orange juice?

(A)25

(B)34

(C)50

(D)67

(E)100

143. In a survey of students, each student selected from a list of 12 songs the 2 songs that the student liked best.If each song was selected 4 times, how many students were surveyed?

(A) 96

(B) 48

(C) 32

(D) 24

(E) 18

80. If x and y are positive integers such that x = 8y + 12, what is the greatest common divisor of x and y ?

(1) x = 12u, where u is an integer.

(2) y = 12z, where z is an integer.

197. The integers m and p are such that 2 < m < p and m is not a factor of p.If r is the remainder when p is divided by m, is r > 1 ?

(1)The greatest common factor of m and p is 2.

(2)The least common multiple of m and p is 30.

以下是2012.3月份寂静中的问题

3. V1. 50个人，20%没有电脑，18%没有手机，6% don't have a laptop or don't have a cellphone.问有多少个人既没有手机也没有电脑 (cflwj)

V2. 我遇到变体,求的既有电脑也有手机.(TSFyfy)

答案：1人只有电脑，2人只有手机，39人既有电脑又有手机。V1答案为8人，V2答案为39人

8.矩形长H,宽W, 外围宽度d, 四个角是圆弧，问长方形与外围的面积比(kdavid1945)

（1）H=2W

（2）矩形周长12d

答案：面积比例=HW/(4Hd+πd^2), 结合两个条件，H=4d, W=2d, 答案选C

45. V1. 折纸题，给出了长方形的长(CD=6, DE = 2)，求AD/DB ratio (vgutsc)

V2. 题目就是沿AC边对折使C点落到BD上为F点，给出条件DF=2 BF=6 求AF/EF (wwc008love)

答案：AD=CD+DE=8（因为是一个长方形，所以AD只不过是折上去了，长度就是长方形的长，不会改变），再根据AD=8 CD=6得出AC=2根号7，再设BD为x，则x^2=DE^2+EB^2，就是 x^2=（2根号7）^2+DE^2，可以求出x=8根号7/7=DB，AD/BD=根号7

我觉得答案是根号2，方法没有错，计算有误啊。。。

求牛人给解答啊！！！马上要考试了，很焦虑

merrymenglu · 发表于 2012-3-9 20:13:17

96. According to the directions on a can of frozen orange juice concentrate, 1 can of concentrate is to be mixed with 3 cans of water to make orange juice.How many 12-ounce cans of the concentrate are required to prepare 200 6-ounce servings of orange juice?

(A)25

(B)34

(C)50

(D)67

(E)100

==============================================
这题不难. 关键在于看懂题目.
首先 1 can of concentrate is to be mixed with 3 cans of water
就是说. 一份orange juice需要4 can

接着. .How many 12-ounce cans 就是说1 can 就是 12ounce

所以要想得出多少个can. 就用总数 200个6ounce相乘. 200*6=1200 ounce.

所以 can的数量就是 1200 /12 = 100 can

最后用 100* (1/4)= 25can
就是A啦~

下面是另外一种解法. 楼主觉得哪个好理解就用哪个把~

【思路】
一份果汁的比例: 濃縮果汁:水=1:3
每份果汁為6 ounce 共需要 200份
需要多少罐，每罐12 ounce的濃縮果汁來做這200份的果汁？
一瓶濃縮原汁和三瓶水混合可以做出一份果汁
200份 6-ounce 果汁
200÷(3+1)=50
但此時單位是6-ounce
題目問的是12-ounce
50÷2=25

深圳的游子 · 发表于 2012-3-9 20:45:08

好长的问题，选择忽略，哈哈

急求！！！！数学疑问

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