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题库 / OG2017Q-DS-236
Each Type A machine fills 400 cans per minute, each Type B machine fills 600 cans per minute, and each Type C machine installs 2,400 lids per minute. A lid is installed on each can that is filled and on no can that is not filled. For a particular minute, what is the total number of machines working?
(1)A total of 4,800 cans are filled that minute.
(2) For that minute, there are 2 Type B machines working for every Type C machine working.
Statement (1) ALONE is sufficient, but statement (2) alone is not sufficient.
Statement (2) ALONE is sufficient, but statement (1) alone is not sufficient.
BOTH statements TOGETHER are sufficient, but NEITHER statement ALONE is sufficient.
EACH statement ALONE is sufficient.
Statements (1) and (2) TOGETHER are NOT sufficient.
题目分析：
设A类型的机器有a台，B类型机器b台，C类型机器c台。其中A、B灌装，C盖盖子。由于题目中说明，所有灌装的罐子均被盖盖子，因此，有400a+600b=2400c，本题求a+b+c的值。
（1） 一分钟总共灌装4800罐，所以有400a+600b=4800，代入得2400c=4800，解得c=2。无法得知a、b的值，所以仅根据条件1无法确定a+b+c的值。
（2） B类型的机器是C类型的两倍，所以b=2c。只有条件2也无法确定a+b+c的值。
结合条件1和条件2，c=2，b=2c=4，代入400a+600b=4800，解得a=6，所以所有的机器总数为a+b+c=2+4+6=12台。题目得解。
因此，本题答案为（C），两个条件结合起来才能解题，任何单独一个均不行。
这题也是读起来感觉吓人，看懂了就是小学算数
A lid is installed on each can that is filled and on no can that is not filled.
400x+600y=4800;2400z=4800;y=2z。
设A、B、C数量分别a、b、c，求a+b+c
条件1： 400a+600b=4800
条件2：2b*600=2400c 得出 b=2c
解：首先，单独1 或者单独2 都不行
其次，1+2， 由2， a+b+c=a+b+0.5b=a+1.5b；由1 a+1.5b=12 （等式两边同除以400）
这样就解出a+b+c=12，问题是并没有利用400a+600b=2400c的条件=_=
A lid is installed on each can that is filled and on no can that is not filled.
刚做完航班时刻表的题，脑补成A+B填充可能大于或小于C的安装频率。。。。
怎么看出C=2的啊？o(╥﹏╥)o
题目中是没有c等于2的，这个是把条件一和二结合起来得到的。
把一二结合，1总共完成了4800个lid,c一次可以完成2400个，所以有2个c. 2 一个c有两个b，就可以知道a的，加起来就是总共的。
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（1） A =0, 3, 6, 9, 12
对应B =8, 6, 4, 2, 0
(2) c=2b， 题目中 c=2 so, b只能等于4
怎么看出C=2的啊？o(╥﹏╥)o
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(1)Not sufficient. There are different combinations of A and B (e.g. 12 machines A's and 0 machine B's OR 2 machine B's and 9 machine A's) that could fill 4800 cans. However, considering that a lid is to be installed on each can, we know that 2 machines C's are working.
(2) For that minute, there are 2 Type B machines working for every Type C machine working
Not sufficient, this only gives us the ratio of machine B to machine C.
为什么这题我选的C但是是错的？