The table above shows the number of residents in each of two age groups who support the use of each type of funding for a city initiative. What is the probability that a person randomly selected from among the 250 residents polled is younger than 40, or supports a type of funding that incudes a tax, or both?
8/25
12/25
3/5
4/5
or 用venn图思维来解 意思是只属于某一块的 即一个圆去掉重叠部分的剩余部分
1、younger than 40 取20+30+30=80
2、or supports a type of funding that incudes a tax 只取10(因为20已经包含在1里了)
3、or both 只取60(因为30已经包含在1里了)
80+10+60=150 150/250=3/5
或者直接用1-P(fees only)
應該是 1 - (Fees only AND =>40) 吧
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韦恩图
或P(AnB)=P(A)+P(B)-P(AB)=P(A)+P(只属于B不属于A)
20+30+30+10+60/250=3/5
我的算法是80/250+30/250+90/250=4/5