请教两条prep数学

luozhan

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 manufacture expects the ratio of the number of defective chips to the total number of the total number of chips in all future shipments to equal the corresponding ratio for the shipping 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

C. 22

D. 24

E. 25

Answer is B.

没有思路,请指教. Thanks.

 

if 500 is the multiple of 100 that is closet to x and 400 is the multiple of 100 that is closet to y, which multiple of 100 is closet to x+y?

(1) x < 500

(2) y < 400

 这条我看不懂是什么意思.

 

[此贴子已经被作者于2008-2-25 9:51:09编辑过]

adamkchim

1. 60,000/( (5,000+12,000+18,000+16,000)/(2+5+6+4))

splendidgary

第二题的意思是：X与所有100的倍数最接近500，Y与所有100的倍数最接近400，问X+Y最接近100的哪个倍数？
1）X<500，没有限制Y的范围，Y可以是351－450，所以X+Y有两个值，insufficient
2）同理也是insufficient
1）＋2）也不行，因为当X＝451，Y＝351，X+Y最接近800；但是当X＝499，Y＝399时，X+Y最接近900
所以这题选E

justsilver

以下是引用splendidgary在2008-2-25 17:52:00的发言：
第二题的意思是：X与所有100的倍数最接近500，Y与所有100的倍数最接近400，问X+Y最接近100的哪个倍数？
1）X<500，没有限制Y的范围，Y可以是351－450，所以X+Y有两个值，insufficient
2）同理也是insufficient
1）＋2）也不行，因为当X＝451，Y＝351，X+Y最接近800；但是当X＝499，Y＝399时，X+Y最接近900
所以这题选E

还是没看懂，＂X与所有100的倍数最接近500＂，有点绕口，什么意思？