Excluding purchases by businesses, the average amount spent on a factory-new car

游客2024-01-13  20

问题 Excluding purchases by businesses, the average amount spent on a factory-new car has risen 30 percent in the last five years. In the average household budget, the proportion spent on car purchases has remained unchanged in that period. Therefore the average household budget must have increased by 30 percent over the last five years. Which of the following is an assumption on which the argument relies?

选项 A、The average number of factory-new cars purchased per household has remained unchanged over the last five years.
B、The average amount spent per car by businesses buying factory-new cars has risen 30 percent in the last five years.
C、The proportion of the average household budget spent on all car-related expenses has remained unchanged over the last five years.
D、The proportion of the average household budget spent on food and housing has remained unchanged over the last five years.
E、The total amount spent nationwide on factory-new cars has increased by 30 percent over the last five years.

答案 A

解析 在解答本题时一定要注意数量关系的变化,我们可以借助简单的数学公式加以推导,设一个家庭开始时在每辆汽车上的花费为x,平均购买汽车数为n,家庭预算为y;在变化后这三项数值分别为x’,n’,y’。则根据本题中的描述,我们很容易得出三个等式,即①:x’=1.3x,②:y’=1.3y,③:nx/y=n’x’/y’。把①、②式同时代入③式,得出n=n’,即每个家庭在这5年当中,平均购买汽车的数量不变。由此分析可知,要使本题的结论成立,那它一定是以(A)选项所描述的内容为assumption。
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