※ 引述《dedust (￾ ︠ ￾臈臈￾ﰩ》之铭言： : On a certain sight-seeing tour, the ratio of the number of women to the : number of children was 5 to 2. What was the number of men on the sight-seeing : tour? : (1) On the sight-seeing tour, the ration of the number of children to the : number of men was 5 to 11. : (2) The number of women on the sight-seeing tour was less than 30 sol: 已知 w:c = 5:2, 求 the number of men on the sight seeing tour (1) c:m = 5:11 ---> the ratio of women to children to men = 25:10:22; however, knowing the ratio does not help us know the exact number of men, so option 1 is invalid. (2) the number of women < 30 (条件不足) 25:10:22 中, 25r <30 ---> 5r < 6 ---> r = 1 therefore, there were 22 men, 25 women, and 10 children. ------------->C : Ans:C : Machines X and Y work a their respective constant rates. How many hours does : it take machine Y, working alone, to fill a production order of a certain : size than machine X, working alone? : (1) Machines 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. Sx = 1/x ; Sy = 1/y 求 Ty - Tx (1) 1/x + 1/y = 3/2 * 1/x 1/y = 3/2x - 1/x = 3/2x - 2/2x = 1/2x y = 2x (2) 1/y *2 = 1/x 2/y = 1/x 2x = y 合并(1) 及(2), 充其量知道 x machine 及 y machine 的比例, 对於两者所需的时间还是没有帮助的------------------------------->(E) : Ans:E ---------------------------------- 我尽力回答了 @_@ --

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