趣味的数学-59
抽屉里放有红袜子和黑袜子2种颜色的袜子。随机抽取2只袜子时，抽出2只袜子都是红色的概率是1/2。 （a）抽屉里的袜子数量至少有几只？ （b）如果黑色袜子的数量是偶数，抽屉里的袜子数量至少又有几只？
【原文】 A drawer contains red socks and black socks. When 2 socks are drawn at random, the probability that both are red is 1/2. (a) How small can the number of socks in the drawer be? (b) How small if the number of black socks is even?
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