作业帮A survey of 100 persons revealed that 72 of them had eaten at restaurant P and that 52 of them had eaten at restaurant Q.Which of the following could not be the number of perspons in the surveyed group who has eaten at both P and A 20B 24C 30 D 50 E
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A survey of 100 persons revealed that 72 of them had eaten at restaurant P and that 52 of them had eaten at restaurant Q.Which of the following could not be the number of perspons in the surveyed group who has eaten at both P and A 20B 24C 30 D 50 E
A survey of 100 persons revealed that 72 of them had eaten at restaurant P and that 52 of them had eaten at restaurant Q.Which of the following could not be the number of perspons in the surveyed group who has eaten at both P and
A 20
B 24
C 30
D 50
E 52
A survey of 100 persons revealed that 72 of them had eaten at restaurant P and that 52 of them had eaten at restaurant Q.Which of the following could not be the number of perspons in the surveyed group who has eaten at both P and A 20B 24C 30 D 50 E
选择A.有28个人没有在P吃过饭,假使这28个人都在Q吃过饭（即都在52人之内）,那么另外的24人肯定都既在P 又在Q 吃过饭,这是最少的人数.因为如果52个人之中没在P中吃过饭的人少于28个,即多于24个,也就是有多于24个的人在P和Q都吃过饭.
B (72+52-100)
选A
一共一百人，52人在Q餐馆就过餐，72人在P餐馆就过餐，如果有20人同时在两个餐馆就餐，那么总人数是114人，不符合题意。
简单的集合问题，全集为100个人，子集合A有72人，子集合B有52人，问你A∩B有多少个人？
72+52-100=24，选 B
选B 24，这段话的意思是:一项100人的调查中，有72个人在饭店P吃，有52，个人在饭店Q吃，问你在两个饭店都吃过的人有多少？用100-（72+52）就可以得到了。
B.24 72+52-100=24 1+2+3=100 1+2=72 2+3=52 ∴2=24