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试题详情

A box at a yard sale contains 3 different china dinner sets, each consisting of 5 plates. A customer will randomly select 2 plates to check for defects. What is the probability that the 2 plates selected will be from the same dinner set?
答案：A

专业教师答疑

2
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2
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Problem Solving

老师这个总的可能数15*14/2！我知道，但为啥分子不是15*4呢（第一个可以选15中任意一个，但第二个只能选那一套里面其余4个了）
6
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6
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Problem Solving

请老师讲一下

问个问题