※ 引述《vitality (有舍才有得...)》之铭言： : 41.Machines X and Y work at theier respective constant rates. How many more : hours does it take machine Y, working alone, to fill a production order of : a certain size than it takes machine X, working alone? : (1)Machine X and Y, working together, fill a production order of this size : in two-thirds the time that machine X, working alone, does. : (2)Machine Y, working alone, fills a production order of this size in : twice the time that machine X, working alone, does. : Ans:E 设总工程为1，X的工作效率为x，Y的工作效率为y (1) 1/(x+y)=(2/3)*(1/x) 化简得 2y=x ...insuff (2) 1/y=2*(1/x) 化简得 2y=x ...insuff 又(1)(2)联立还是只有一条方程式 ...insuff : 76.Is the integer K divisible by 4? : (1) 8K is disvisible by 16. : (2) 9k is disvisible by 12. : Ans:B (1)8K/16=K/2...0 只知道K能被2整除 ...insuff (2)9K/12=3K/4...0 由於前面的3不是4的倍数，所以後面的K肯定能被4整除...suff : 93.If the integer n is greater than 1, is n equal to 2? : (1) n has exactly two positive factors. : (2) The difference of any two distant factors of n is odd. : 这题不懂的是第二个选项 : 如果n=4 factors有1.2.2或是1.4 这样2-1或4-1 不也是odd的吗? : Ans: B (1)刚好只有2个因数的整数 2,3,5,7,11....insuff (2)正整数有2种，奇数跟偶数 奇数:因数包含本身和1，2者相减必定是偶数 ex:3-1,5-1,7-1... 超过2的偶数:因数包含本身和2，2者相减必定也是偶数 ex:4的因数:1,2,4 =>4-2 6的因数:1,2,3,6 =>6-2 正整数排除以上只剩2了...suff --

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