推 dolphin100:謝謝^^ 08/18 15:29
※ 引述《dolphin100 (得分100~~YA)》之銘言：
: A total of 100 customers purchased books at a certain bookstore last week.
: If these customers purchased a total of 200 books, how many of the customers
: purchased only 1 book each?
: (1) None of the customers purchased more than 3 books.
: (2) 20 of the customers purchased only 2 books each.
: 答案是C ，可是我覺得很怪，搞不懂
買1本 x 人 , 買2本 y人 買3本 z人
1)沒人買超過三本 => x + y +z =100 x+2y+3z=200
不充分
2)20人買二本
不充分
1+2) y = 20
x +z = 80
x + 40 +3z = 200
可以求出只買一本的
--
※ 發信站: 批踢踢實業坊(ptt.cc)
◆ From: 218.166.11.180