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  3. A man has 53 socks in his drawer: 21 identical blue, 15 identical black and 17 i

A man has 53 socks in his drawer: 21 identical blue, 15 identical black and 17 i

游客2023-10-16  41
问题 A man has 53 socks in his drawer: 21 identical blue, 15 identical black and 17 identical red. The lights are fused and he is completely in the dark. How many socks must be taken out to make 100 percent certain he has a pair of black socks?
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答案 40 socks
解析 (这道题的意思是至少几次可取到一双黑袜子。假设在取第一只黑袜子时已将蓝色和红色的袜子全部取过，则第21+17+1=39只袜子是黑色，之后任取一只都可与之配成一双黑袜。所以答案为39+1=40只。)
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