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Set P consists of all the positive even integers less than 14,and set Q consists of all the positive multiples of 3 less than 21.Set R consists of all members that are either in set P or set Q.How many members of set R are even?(A) 6(B) 7(C) 9(D) 10(E) 12我怎么觉得有18个 选哪个

分类: 作业答案 • 2022-01-02 16:27:00
问题描述：

Set P consists of all the positive even integers less than 14,and set Q consists of all the positive multiples of 3 less than 21.Set R consists of all members that are either in set P or set Q.How many members of set R are even?
(A) 6
(B) 7
(C) 9
(D) 10
(E) 12
我怎么觉得有18个 选哪个

答

P整的偶数级（小于14）2.4.6.8.10.12.
Q3的倍数（小于21），3.6.9.12.15.18.
去掉重复的，应该是10个

答

10个，选D
P的范围是所有小于14的偶整数，也就是2、4、6、8、10、12
Q的范围是所有小于21的3的倍数，也就是3、6、9、12、15、18
其中PQ两者都含有的就有6和12；
那么R的值不是在P里的，就是在Q里的，那就是2、3、4、6、8、9、10、12、15、18，一共有10个。
这是我的解答。

答

P={2,4,6,8,10,12}
Q={3,6,9,12,15,18}
R={2,3,4,6,8,9,10,12,15,18}
其中偶数个数是7,故选B

答

选D 有10个 分别是2 3 4 6 8 9 10 12 15 18

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