请教GWD数学题

xuromeo

请大家帮帮我 看看怎么做啊？数学一般错几题可以达到50？
if p is the product of the integers from 1to 3o,inclusive,what is the greatest integer k for which 3 k次方 is a fator of p?
A10 B12 C14 D16 E18
正确答案C
Each of the 30boxes in a certain shipment weighs either 10pound or 20pounds,and average weight of the boxes in the shipment is18pounds.if the average weight of the boxes in the shipment is to be reduced to 14pounds by removing some of the 20pound boxes,how many 20pound boxes must be removed?
A4 B6 C10 D20 E24

four staff members at a certain company worked on a project .The amount of time that the four staff members worked on the project were in the ratio 2to 3to 5 to 6.If one of the four staff members worked on project for 30hours,which of the following can not be the total number of hours that the four staff members worked on the project?
A80 B96 C160 D192 E 240

Of the 500 business people surveyed,78percent said that they use their lap top computers at home 65percent said they use them in hotels,and 52percent said they use them both at home and hotels.How many of the business people surveyed said that they do not use their laptop either at home or in hotel?
A45 B55 C65 D95 E130
正确答案A

tinahuang95

1、    3的倍数  3 6 9 12 15 18 21 24 27 30
分别为（倍数）1 1 2 1   1    2   1   1   3   1 =14个

tinahuang95

2、首先算出 之前有6个10磅和24个20磅的
最后平均是14磅
设最后剩X个20磅的
14*（6+X）=60+20X
X=8/3
你确定给的数据是对的？ 最后是reduced to 还是reduced by?

tinahuang95

3、总共工作16倍时间
设30小时是2倍时间 30/2*16
是3倍时间 30/3*16
5倍时间30/5*16
6倍时间 30/6*16

看哪个不是的

tinahuang95

4、 这种题 最简单方法就是画图

                    HOME     NON-HOME
HOTEL             1          2

NON-HOTEL    3           4
1+3=78%  
1=52%
3=26%

1+2=65%
3+4=35%
因为3=26%
所以4=9%*500=45

zwjun1111

呃  第二题可能是这样做

30boxes 的总重量为30*18
设被拿走的20P的boxes为X，剩下的boxes数量为30-X
则被拿走的重量为20*X
所以
（30*18-20*X）/30-X=14

得出X=20

tinahuang95

呃  第二题可能是这样做

30boxes 的总重量为30*18
设被拿走的20P的boxes为X，剩下的boxes数量为30-X
则被拿走的重量为20*X
所以
（30*18-20*X）/30-X=14

得出X=20

-- by 会员 zwjun1111 (2011/10/28 11:59:20)

你这是对的~ 不过为什么我那个方法算出来不对呢？

zwjun1111

呃  第二题可能是这样做

30boxes 的总重量为30*18
设被拿走的20P的boxes为X，剩下的boxes数量为30-X
则被拿走的重量为20*X
所以
（30*18-20*X）/30-X=14

得出X=20

-- by 会员 zwjun1111 (2011/10/28 11:59:20)

你这是对的~ 不过为什么我那个方法算出来不对呢？

-- by 会员 tinahuang95 (2011/10/28 12:22:32)

也可以呀，你应该是算错了哦  算出来是X=4   不过题目问的是remove的个数   而你设的未知数是剩下的个数   所以还要24-4=20^_^

xuromeo

谢谢 是reduce to 14 pounds