问道prep上的题

disaka

Shipment    Number of Defective Chips in the Shipment           Total number of chips in the shipment
  S1                       2                                                                           5,000
  S2                       5                                                                         12,000
  S3                       6                                                                         18,000
  S4                       4                                                                         16,000
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?

答案：20

打了好半天，希望有人理我哈~

微笑红尘

题目中有“to equal the corresponding ratio for shipments S1, S2, S3, and S4 combined”

那就顺便combine一下S1,S2,S3, and S4
Sum(defective chips)=2+5+6+4=17.
Sum(total chips)=5000+12000+8000+16000=51000.
现有60,000 chips,若equal the corresponding ratio，则
17/51000=x/60000 =>x=20

碰巧我也刚做这道题

disaka

太有才了...感谢