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请教两道PREP数学题

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楼主
发表于 2008-4-27 00:03:00 | 显示全部楼层

请教两道PREP数学题

 

3. 196-!-item-!-187;#058&000141

How many different prime numbers are factors of the positive integer n ?

(1) Four different prime numbers are factors of 2n.

(2) Four different prime numbers are factors of n^2.

答案 B 但是我觉得(1)也充分

3. 196-!-item-!-187;#058&000141

How many different prime numbers are factors of the positive integer n ?

(1) Four different prime numbers are factors of 2n.

(2) Four different prime numbers are factors of n^2.

答案 B 但是我觉得(1)也充分

34  2927-!-item-!-187;#058&003024

During an experiment, some water was removed from each of 6 water tanks. If the standard deviation of the volumes of

water in the tanks at the beginning of the experiment was 10 gallons, what was the standard deviation of the volumes of

water in the tanks at the end of the experiment?

(1) For each tank, 30 percent of the volume of water that was in the tank at the beginning of the experiment was removed

during the experiment.
(2) The average (arithmetic mean) volume of water in the tanks at the end of the experiment was 63 gallons.

谢谢先!

沙发
 楼主| 发表于 2008-4-27 01:29:00 | 显示全部楼层

谢谢楼上MM

第二题能说说A是怎么算的么?意见standard deviation我就蒙了

板凳
 楼主| 发表于 2008-4-27 08:33:00 | 显示全部楼层
谢谢楼上,一觉醒来,突然想到第二题的A是非常容易算出来的,昨天怎么绕都没绕出来,汗
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