京都大学 情報学研究科 知能情報学専攻 2019年2月実施 専門科目 F2-2

标签：

• Kyoto-University
• Fundamentals

Author

祭音Myyura (with GPT 5.5)

Description

Minister X claims that his policies for preventing motorbike accidents caused by young drivers are successful: the number of young drivers causing motorbike accidents has halved. His political opponent, Mr. Y, argues on the other hand that the proportion of motorbike accidents that are caused by young drivers has increased from 20% to 40%.

(1) Explain briefly why Minister X's and Mr. Y's assertions do not contradict with each other.

(2) is the initial total number of accidents (with both young and old drivers), and is the total number of accidents after Minister X's policies. Express in terms of .

Kai

Let the initial total number of accidents be .
Since young drivers initially caused of all accidents, the initial number of accidents caused by young drivers was

Minister X says that this number has halved. Therefore, after the policies, the number of accidents caused by young drivers is

On the other hand, Mr. Y says that this number is now of the total number of accidents. Hence,

Solving this equation, we obtain

Therefore,

(1)

Minister X's and Mr. Y's assertions do not contradict each other because Minister X is talking about the absolute number of accidents caused by young drivers, while Mr. Y is talking about their proportion among all accidents.

The number of accidents caused by young drivers has decreased from to , but the total number of accidents has decreased even more, from to . Thus, the proportion of accidents caused by young drivers can increase from to .

(2)