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