题目

In a 200 member club consisting of men and women, exactly 20% of men and exactly 25 % women are homeowners.


Quantity A

Least number of members who are homeowners


Quantity B

41

选项

A.

Quantity A is greater.

B.

Quantity B is greater.

C.

The two quantities are equal.

D.

The relationship cannot be determined from the information given.

解析

设男性成员有\(x\)人,则女性成员有\(200 - x\)人。 男性中有房者的人数为\(0.2x\),女性中有房者的人数为\(0.25(200 - x)=50 - 0.25x\)。 那么总的有房者人数\(y = 0.2x+50 - 0.25x=50 - 0.05x\) 要使得\(y\)最小,也就是要让\(x\)尽可能大。 因为人数\(x\)的取值范围是\(0\leq x\leq200\),且\(x\)为整数,当\(x = 200\)时(即全是男性成员这种极端情况),此时有房者人数\(y = 50-0.05\times200=50 - 10=40\) 当\(x = 0\)时(即全是女性成员这种极端情况),\(y=50\) 但是由于俱乐部由男性和女性组成,所以\(x\)的取值在\((0,200)\)之间。 我们可以通过计算\(y = 50-0.05x\)在\(x = 180\)(假设男性成员有180人)时的值来进一步确定范围 \(y=50 - 0.05\times180=50 - 9 = 41\) 所以有房者最少人数为\(41\),即\(A = B\),答案选C。
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