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

Author

itsuitsuki

Description (English)

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

(1) The total number of accidents has also decreased along with the young drivers', but faster.

(2) Let the young drivers' accidents be before and after. Then,

Hence

and thus .