一道统计问题（英文）

题目

一道统计问题（英文）
According to a survey of American households,the probability that the residents own 2 cars if annual household income is over $25,000 is 80%.Of the households surveyed,60% had incomes over $25,000 and 70% had 2 cars.The probability that theresidents of a household do not own 2 cars and have an income over $25,000 a year is_______.

答案

因为60%的收入超过25,000,而收入超过25,000的人中有80%的人拥有2辆车,所以60% x 80% = 48%的人满足条件收入超过25,000并且有2辆车.那么收入超过25,000但没有车的人就是60% - 48% = 12%的人