prep-ds1-50 请教解体思路***急***

wj37044

50.    4230-!-item-!-187;#058&003784

A construction company was paid a total of $500,000 for a construction project.  The company's only costs for the project were for labor and materials.  Was the company's profit for the project greater than $150,000 ?

 

(1)  The company's total cost was three times its cost for materials.

 

(2)  The company's profit was greater than its cost for labor.

key:c

但我选的是E

因为1+2=>   L=2M 和 p>L 而问题推出的是M+L<350,000.

所以我觉的1+2推不出.

请哪为能提供正确思路?????

wj37044

还有一题

46.    3960-!-item-!-187;#058&003582

How many hours did it take Helen to drive from her house to her parents' house?

 

(1)  Helen's average speed on this trip was 72 kilometers per hour.

 

(2)  If Helen's average speed on this trip had been 8 kilometers per hour greater, it would have taken her 1 hour less.

key:c

但我选的是E,同问??????

jet_chan

第一题，500000-3x>2x,得出x<100000，那么profit=500000-3x则>200000，当然也大于150000，答案选C

第二题，72t=80(t-1)，得出t=10，答案选C

DorothyWRSC

第一题：（1）告诉我们M花了167000，L和P和是333000

（2）告诉我们P大于L

两个合起来告诉我们P是大于167000的，所以肯定大于150000

所以选C没问题

wj37044

第一题我想通了,我没有完全代进去,m<100,000 所以3m=m+l<300,000

选c

但第二题还想不通

kaito_2000

一、总收入500k，投入两部分：M和L。问，利润是不是大于150k。

[1]说，总支出是M的三倍，所以M=500*1/3，L+P=500*2/3。

[2]说，利润比L大。

联立，即利润>500*1/3>150k。

二、问，H从家里开车到父母家要多久。

[1]说，H时速72K/H。

[2]说，如果H时速提高8K/H，可以少用1小时。

联立，设总距离为a，即a/72-a/(72+8)=1，可解得a，根据H的时速可得到时间。

[此贴子已经被作者于2009-4-5 22:30:19编辑过]

DorothyWRSC

第二题楼上解释了，我就不再敲一遍了，呵呵

wj37044

谢了

jet_chan

我觉得第一题的1）是意思是说total cost是M的三倍，total cost应该是M+L，不应该是500000啊，Profit应该是500000减去（m+L)，500000是总的钱