[求助]DS_10

黄公子

10.   719-!-item-!-187;#058&000515

Of the 800 students at a certain college, 250 students live on campus and are more than 20 years old.  How many of the

 

800 students live on campus and are 20 years old or less?

 

(1)  640 students at the college are more than 20 years old.

 

(2)  60 students at the college are 20 years old or less and live off campus.

答案: C

做也会做，但是这种题目思路不清晰，请教大家如何解此类题.

文氏图可以么？好像有4个集合阿.谢谢！

youyou3941

画图

             campus      off campus

大于20岁的                              640

小于等于20的  a              60

基本是这样，但是我不会传图将就看了吧，求a

黄公子

明白了，其实等于画个表格而不是图吧