[请求][问题]几道Problem solving题! [复制链接]

fernandochang
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电梯直达

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发表于 2003-6-9 22:58:48 |只看该作者 |倒序浏览

都是Official Guide的题目....我是数学白痴.....请见谅!
367.Which of the following is equal to the average(arithmetic mean) of (x+2)的2次方 and (x-2)的2次方?
(A)x的2次方
(B)x的2次方+2
(C)x的2次方+4
(D)x的2次方+2x
(E)x的2次方+4x
A):C

368.If x的4次方+y的2次方=100 then the greatest possible value of x is between
(A)0 and 3
(B)3 and 6
(C)6 and 9
(D)9 and 12
(E)12 and 15
A):B

369.During a car trip, Maria stopped to rest after she traveled 1/2 of teh total distance to her destination. She stopped again after she traveled 1/4 of the distance remaining between her first stop and her destination, and then she drove the remaining 120 miles to her destination. What was the total distance, in miles, from Maria's starting point to her destination?
(A)280
(B)320
(C)360
(D)420
(E)480
A):D

379. An arithmetic sequence is a sequence in which each term after the first is equal to the sum of the preceeding term and a constant. If the list of numbers shown above is an arithmetic sequence, which of the following must also be an arithmetic sequence?
I.2p, 2r, 2s, 2t, 2u
II.p-3, r-3, s-3, t-3, u-3
III.p的2次方, r的2次方,s的2次方,t的2次方,u的2次方
(A)I only
(B)II only
(C)III only
(D)I and II
(E)II and III
A):D

381. Dick and Jane each saved $3,000 in 1989. In 1990 Dick saved 8% more than in 1989, and together he and Jane saved a total of $5,000. Approximately what percent less did Jane save in 1990 than in 1989?
(A)8%
(B)25%
(C)41%
(D)59%
(E)70%
A):C

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Zter
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沙发

发表于 2003-6-11 11:41:52 |只看该作者

[问题]您是真不会还是...？看来您得努力了。

367
(x+2)^2=x^2+4x+4
(x-2)^2=x^2-4x+4
(x+2)^2+(x-2)^2=2x^2+8 求平均值要再除以2，得几？

368
要让x最大，则必让y^2最小，那就是y^2=0.然后看看x取值多少x^4能够不超过100，显然x的最大值在3－4之间。

369 设距离为D
第一次stop时距终点 1/2D
第2次stop时距第一次stop点 1/2D×1/4=1/8D，距终点D－1/2D-1/8D=3/8D=120miles,D=320,答案是不是有问题？

379
这里定义的算术序列其实就是等差数列。题目是说如果p r s t u是这样的数列，下面哪个也是？显然有平方项的不会是。

381
得算一下。In 1990 Dick saved 3000×（1＋8％）＝3240。则Jane save in 1990 ＝5000-3240＝1760，这比1989年的3000少了1240，也就是1240/3000＝41.33％。

一捧细沙，本来可以好好地捧在手上，可是你偏想用力地把它攥在手心。结果，就在你用力的同时，它却从你的指间悄悄滑落。

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