请教几道PP数学

jimoshanlin

167 A certain circular area has its center at point P and has radius 4, and points X and Y lie in the same plane as the circular area.  Does point Y lie outside the circular area?

(1)  The distance between point P and point X is 4.5.

(2)  The distance between point X and point Y is 9.

C

这个题请NN解释下

 

182.  If m and r are two numbers on a number line, what is the value of r ?

(1)  The distance between r and 0 is 3 times the distance between m and 0 .

(2)  12 is halfway between m and r.

E

 我觉得1，2结合才可以求出唯一的r。不明白为什么选E

 

109. 

Marta bought several pencils.  If each pencil was either a 23-cent pencil or a 21-cent pencil, how many 23-cent pencils did Marta buy?

(1)  Marta bought a total of 6 pencils.

(2)  The total value of the pencils Marta bought was 130 cents.

B

我觉得选C，23X+21Y=130，X+Y=6。即使X，Y都为整数，可以只用（2）就求出X，Y？

 

shipment    No. of defective chips   Total no. of chips

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?

 

(A) 14

(B) 20

(C) 22

(D) 24

(E) 25

这个题应该意思理解错误，怎么也算不出来20。。。。。。。。

愁予

1.由1 p与x的距离与ｙ无关，不行。由２ｘ与ｙ的距离与园无关，不行。１和２一起，三角形两边和大于第三边ｐｘ＋ｐｙ＞ｘｙ，ｐｙ＞４．５，ｙ一定在园外。

２。ｍ，ｒ可以分居原点两边，也可以在同一边。

３。２３ｘ＋２１ｙ＝１３０只有一个整数解

４。期望值就是一个变量输出值得平均数。ｔｏｔａｌ的和／defective 的和＝期望比率３０００。

愁予

1.由1 p与x的距离与ｙ无关，不行。由２ｘ与ｙ的距离与园无关，不行。１和２一起，三角形两边和大于第三边ｐｘ＋ｐｙ＞ｘｙ，ｐｙ＞４．５，ｙ一定在园外。

２。ｍ，ｒ可以分居原点两边，也可以在同一边。

３。２３ｘ＋２１ｙ＝１３０只有一个整数解

４。期望值就是一个变量输出值得平均数。ｔｏｔａｌ的和／defective 的和＝期望比率３０００。

jimoshanlin

多谢楼上解答！

第二题中， 12 is halfway between m and r, 这里的12只是距离，不是number 12吗？很容易混淆，题目没说清楚啊~~~

23X+21Y=130 只有一个整数解，怎么看呢？是要一个个算吗？现场没时间啊~~~