Your sock drawer contains ten pairs of white socks and ten pairs of black socks. If you’re only allowed to take one sock from th

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问题 Your sock drawer contains ten pairs of white socks and ten pairs of black socks. If you’re only allowed to take one sock from the drawer at a time and you can’t see the color of the sock you’re taking until you’ve taken it, how many socks do you have to take before you’re guaranteed to have at least one matching pair?

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答案Three socks.

解析 (假设第一次取到白色袜子,若第二次是白色则可配成一对;若是黑色需要继续取,第三次不论黑白均可与之前取到的袜子配成一对。所以至少两次,至多三次就可取到可配对的袜子。)
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