急问一道prep数学!!!

没有人 · 发表于 2010-3-5 21:26:29

if bob produces 36 or fewer items in a week,he is paid x dollars per item. If bob produces more than 36 items in a week, he is paid x dollars per item for the first 36 items and 1.5times that amount for each additional item. How many items did bob produce last week.

1, last week bob was paid a total of 480 dollars for the items that be peoduced that week
2, this week bob produced 2 items more than last week and was paid a total of 510 dollars for the items that he produced this week.

why the answer is E, please help me...

true · 发表于 2010-3-5 22:23:59

36items是分界点。

条件1，
假设做了A个东东。
如果A<36则，Ax=480.
如果A=36则，这个不需求了。
如果A>36则，Ax+（A-36）1.5x=480.

条件2，
假设他做了B个东东。
和条件1一样，
B+2<36,(B+2)x=510
B+2=36,B=34个。
B+2>36, 36x+(B+2-36)=510.

两个条件都不充分，

看看结合的情况.
设生产产品为C个。
如果C+2<=36
则， Cx=480 和（C+2）x=510 =>C=32

如果C<=36,但C+2>36
则，Cx=480 和 36x+(C+2-36)1.5x=510 =>C=34.3这个不算吧。

如果C>36
则，36x+（C-36）1.5x=480和36x+（C+2-36）1.5x=510 =>C=44

就是E了。我也搞错了。算得挺麻烦。

急问一道prep数学!!!

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