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题库 / Prep2007E1-PS-89
A company has two types ofmachines, type R and type S. Operatingat a constant rate, a machine of type R does a certain job in 36 hours and amachine of type S does the same job in 18 hours. If the company used the same number of eachtype of machine to do the job in 2 hours, how many machines of type R wereused?
3
4
6
9
12
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do the job in 2 hours----=2h 而不是
“If the company used the same number of each type of machine”意思是：共同完成
设这个任务为W, 机器量为n
(W/36+W/18)*2n=W
n=6
If the company used the 【same number】 of each type of machine