[求助]请教PREP第二套里的一道数学题（应用题）

sudashui

这道题我想来想去都不知道是个什么意思，请各位帮忙看一下啦。

A computer chip manufacturer expects the ratio of the number of defective chips to the total number of chips in all future shipments to equal the corresponding ratio for shipments S1.S2.S3 and S4 combined, as shown in the table above. What's the expected number of detective chips in a shipment of 60000 chips？

shipments             number of defective chips       total number of chips in the shipment       

S1：                             2                                               5000

S2:                               5                                                12000

S3                                6                                                18000

S4                                4                                                16000

                                    ?                                                 60000

备选答案：14、20、22、24、25   答案：20

我想了下，是要列个方程式，然后把已知数代入解出这两者的关系吗？但我代数到y=ax+b算出a.b的值，然后再代60000进去方程式算x，好像也不对。不会是二元方程式吧..

[此贴子已经被作者于2008-12-19 16:07:54编辑过]

xiaoy791

(2+5+6+4)/(5000+12000+18000+16000)=?/60000

then to get ?=20

sudashui

以下是引用xiaoy791在2008-12-19 22:47:00的发言：

(2+5+6+4)/(5000+12000+18000+16000)=?/60000

then to get ?=20

谢谢！