求 大神解答

txt1221

　　400 people answered questions 1 and 2 for yes or no. 340 people said yes to question 1 and 180 people said yes to question 2. n is the number of people said yes to both questions. which of the following can be n:
　　100
　　125
　　140
　　175

普渡哥

100

konatsu

125  140  175
全集是400，n是340和180这两个集合的交集
最大的n：340包含180，180
最小的n：尽量不重合，340+180-400=120