求解GWD第9套若干题~

nikkoyu · 发表于 2010-9-1 10:14:22

Q17:

A certain list consists of 21 different numbers.If n is in the list and n is 4 times the average (arithmetic mean) of the other 20 numbers in the list, then n is what fraction of the sum of the 21 numbers in the list?

A. 1/20 B. 1/6 C. 1/5 D. 4/21 E. 5/21

Q20:

	Favorable	Unfavorable	Not Sure
Candidate M	40	20	40
Candidate N	30	35	35

The table above shows the results of a survey of 100 voters each responded “favorable” or “unfavorable” or “not sure” when asked about their impressions of candidate M and of candidate N.What was the number of voters who responded “favorable” for both candidates?
(1）The number of voters who did not respond “favorable” for either candidate was 40.
(2)The number of voters who responded “unfavorable” for both candidates was 10.
答案为什么选A而不选C？

Q32:What is the remainder when the positive integer x is divided by 8?
(1)When x is divided by 12, the remainder is 5.
(2)When x is divided by 18, the remainder is 11. 请问答案为什么选E？

Q36: If x, y, and k are positive numbers such that [X/(X+Y)](10) + [Y/(X+Y)](20) = k and if x < y, which of the following could be the value of k?
A.10 B.12 C.15 D.18 E.30

Leliolevine · 发表于 2010-9-1 10:46:35

Q17:

A certain list consists of 21 different numbers.If n is in the list and n is 4 times the average (arithmetic mean) of the other 20 numbers in the list, then n is what fraction of the sum of the 21 numbers in the list?

A. 1/20 B. 1/6 C. 1/5 D. 4/21 E. 5/21
n/4就是其他20个数的平均数，其他20个数的和为5n，n/（n+5n）=1/6

Q20:

	Favorable	Unfavorable	Not Sure
Candidate M	40	20	40
Candidate N	30	35	35

The table above shows the results of a survey of 100 voters each responded “favorable” or “unfavorable” or “not sure” when asked about their impressions of candidate M and of candidate N.What was the number of voters who responded “favorable” for both candidates?
(1）The number of voters who did not respond “favorable” for either candidate was 40.
(2)The number of voters who responded “unfavorable” for both candidates was 10.
答案为什么选A而不选C？

从（1）中得知the number of voters who respond favorable for either candidate was 100-40=60...两个都选就是交集，40+30-60=10

Q32:What is the remainder when the positive integer x is divided by 8?
(1)When x is divided by 12, the remainder is 5.
(2)When x is divided by 18, the remainder is 11. 请问答案为什么选E？
(1)17/8 余1， 29/8余5
(2)同理
(1)+(2)x=12n+5 x=18m+11 12n+5=18m+11 n=(3m+1)/2 要保证n是整数，则m为奇数。。
18*(2q+1)+11满足(1)(2) 当q为奇数是，除8余1，当q为偶数是，余数为5

Q36: If x, y, and k are positive numbers such that [X/(X+Y)](10) + [Y/(X+Y)](20) = k and if x < y, which of the following could be the value of k?
A.10 B.12 C.15 D.18 E.30

-- by 会员 nikkoyu (2010/9/1 10:14:22)

10x/(x+y)+20y/(x+y)=k 10x+20y=kx+ky x/y=(k-20)/(10-k)因为x<y且都是正数，所以x/y 范围是(0,1)验证一下选18

nikkoyu · 发表于 2010-9-1 16:22:48

噢~小灰太狼，真的太谢谢你了！
哈，几乎每次都是你帮忙解答问题！真的灰常感激！

Leliolevine · 发表于 2010-9-1 16:52:04

一起讨论互相进步。。加油加油啦。。

噢~小灰太狼，真的太谢谢你了！
哈，几乎每次都是你帮忙解答问题！真的灰常感激！

-- by 会员 nikkoyu (2010/9/1 16:22:48)

nikkoyu · 发表于 2010-9-1 17:21:07

小灰灰，我还有两题想请教你。怎么想都想不明白，而且网上的讨论也看不懂~
1）The sides of a square region, measured to the nearest centimeters, are 6 centimeters long.The least possible value of the actual area of the square region is

A.36.00 sq cm B.35.00 sq cm C.33.75 sq cm D.30.25 sq cm E.25.00 sq cm

2）What is the remainder when the positive integer n is divided by the positive integer k, where k > 1?(1)n = (k+1)³
(2)k = 5 为什么选A？

Leliolevine · 发表于 2010-9-1 17:26:35

第一题least possible value of the actual area 指的是面积的可能值中最小的值。首先接近6厘米的边长范围是[5.5，6.5] 最小的值就是5.5^2啦。。30.25
第二题(1)要展开的n=k^3+3k^2+3k+1 加上k>1这个条件，n除以k余1 所以选A

nikkoyu · 发表于 2010-9-1 17:40:00

哦，我明白了~ 原来是题意理解错了。Least我还以为是最不可能的那个。谢拉！

BY TEH WAY。。。

Is r > -1?
(1)r > -5
(2)r < 16 为什么答案要选E而不选A？
r > -5不是包括r > -1的情况吗？

求解GWD第9套若干题~

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