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[请求][问题]og上数学问题请教! [复制链接]

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发表于 2003-6-16 18:32:47 |只看该作者 |倒序浏览
og上解释看不懂! 请大家帮忙谢谢!
385. For how many integers n is 2 的 n 次方=n 的2次方?
(A)None
(B)1
(C)2
(D)3
(E)More than 3
A):C

394. Right traingle PQR is to be constructed in the xy-plane so that the right angle is at P and PR is parallel to the x-axis. The x- and y-coordinates of P, Q, and R are to be integers that satisfy the inequalities -4≦x≦5 and 6≦y≦16. How many different triangles with these properties could be constructed?
(A)110
(B)1,100
(C)9,900
(D)10,000
(E)12,100
A):C

404. A square countertop has a square tile inlay in the center, leaving an untiled strip of uniform width around the tile. If the ratio of the tiled area to the untiled area is 25 to 39, which of the following could be the width, in inches, of the strip?
I. 1 又1/2
II. 3
III.4 又1/2
(A)I only
(B)II only
(C)I and II only
(D)I and III only
(E)I, II, and III
A):E

416. If a certain sample of data has a mean of 20.0 and a standar deviation of 3.0, which of the following values is more than 2.5 standard deviations from the mean?
(A)12.0
(B)13.5
(C)17.0
(D)23.5
(E)26.5
A):A

417.Which of the following is the least positive integer that is divisible by 2,3,4,5,6,7,8,and 9?
(A)15,120
(B)3,024
(C)2,520
(D)1,890
(E)1,680
A):C
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沙发
发表于 2003-6-16 18:52:31 |只看该作者

417

挨个除一下就行。
别的没看懂,深受打击。
爱情有没有终点?

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板凳
发表于 2003-6-17 09:18:21 |只看该作者

416

more than 2 standard deviations from the  mean 是指与20相差大于2.5* 3,i.e.more than 20+2.5*3 or less than 20--2.5*3, so  A is  the answer.
A cent of mirth is worth  a dollar of grief.

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地板
发表于 2003-6-17 09:26:21 |只看该作者

394

P is the right angle,P的取值范围是X:-4到5,共10种,Y:6到16,共11种.所以10*11=110
因为PRP平行于X轴,此时R有10种取值,Q有9种取值.
所以共:110*10*9=9900
A cent of mirth is worth  a dollar of grief.

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RE: [请求][问题]og上数学问题请教! [修改]
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