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向大家求助数学题！感谢好心的你！
本人做题时遇到一些问题搞不懂，快要考试了，特此向大家求助，万分感谢！
1、
shipment
| Number of defective chips in the shipment
| Total number of chips in the shipment
| S1
| 2
| 5000
| S2
| 5
| 12000
| S3
| 6
| 18000
| S4
| 4
| 16000
|
A computer chip manufacture 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 60000 chips?
A.14
B.20
C.22
D.24
E.25
答案是D
2、Pumps A,B and C operate at their respective constant rates. Pumps A and B, operating simultaneously, can fill a certain tank in 6/5 hours; Pumps A and C, operating simultaneously, can fill the tank in 3/2 hours; and Pumps B and C, operating simultaneously,can fill the tank in 2 hours. How many hours does it take pumps A,B and C, operating simultaneously, to fill the tank?
A.1/3
B.1/2
C.2/3
D.5/6
E.1
答案是E
3、If n and y are positive integers and 450y=n^3,which of the following must be an integer?
一、y/(3*2^2*5) 二、y/(3^2*2*5) 三、y/(3*2*5^2)
A.None
B.一
C. 二
D.三
E.all
答案是B
万分感谢！
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