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Thursday, September 9, 2010

Some counting

Math 110 students are learning counting, now here is a suitable problem from HKgolden.
Problem. There are 2 guys, A and B, and there is a box containing 9000 balls numbered 1000, 1001, ..., 9999 respectively. Suppose A has chosen a ball with replacement, what is the probability that B chooses a ball with no digit in common with that of A? (Say if A has chosen 1234, then B will choose a number that does not contain any digit in {1, 2, 3, 4})
張貼者： 於
標籤：

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