这道题疑问在审题上。。
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 is the expected number of defective chips in a shipment of 60,000 chips?
A 14 B 20 C22 D24 E 25 Key:B
(expect the ratio=the corresponding ratio combined)难道不是(2/500)+(5/12000)…这样加起来的和为expect ratio吗? 但是答案是(2+5+..)/(5000+12000...)这样算法的。。。
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