将3支红筷子，9支黄筷子，18支绿筷子，2支白筷子和1支黑筷子放在一个布袋里，至少摸 支才能保证有两双颜色相同的筷子．
× = ×= × =1．
35× =0.5× =× =6÷ =1．
任何一个数（零除外）与它的倒数的乘积是1． ．
× =× =× =9× =1．
和 互为倒数．
× = ×
= × =1．
× =6÷ =1．
× =
× =
× =9× =1．
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