Math Prep question

gpc7109

哪位ＮＮ人可以帮解答下面的ＰＲＥＰ的一道数学题．我看了好长时间了．．．

Working alone at its own constant rate, amachine seals K cartons in 8 hours, and working alone at its own constant rate,Asecond machine K cartons in 4 hours. If the two machine each working at its own constant rate and for the same period of time, together sealed a certain number of cartons, what percent of the cartons were sealed by the machine working at fater rate ?

 The answer is 66.1/3 something Percent .

qiuhailing01

题: 机器A8小时能封K个,即速率是每小时K/8; 机器B4小时能封K个,即速率是每小时K/4;问两台机器同时工作相同时间(设为H)封一定数量的箱子,速率高的那台所封的箱子占两台机器所封箱子的比率.

解: 速率较快的是B, 所以: (K/4)H/{(K/8)+(K/4)]H = 2/3 (即66.1/3%)

h5641

小弟不是NN, 我會的都是CD教我的.

Machine A 的工作時間　1/8
Machaine B 的工作時間 1/4

( 1/8 + 1/4) * X =1

X= 8/3  代表一起工作需要的時間

而　Machine B 的working rate 是　faster 的

所以　8/3 * 1/4 = 2/3  代表　Machine B 所佔有的percentage.

gpc7109

好感谢两位的及时指点，记在心里了．祝二位申请到理想的学校，相信你们的 kindness 会在生活上给你们带来好运的！