推 danis31 :如果用反推咧 1-黑黑-白白 有比較簡單嗎?(好像沒差) 05/29 01:06
這題想了很久，就是沒什麼頭緒，不知道有沒有什麼關鍵呢?
A box contains p white balls and q black balls. Beside the box there is a pile
of black balls. Two balls are taken out from the box. If they are of the same
color, a black ball from the pile is put in the box. If they are of different
colors, the white ball is put back into the box. This procedure is repeated
until the last pair of balls is removed from the box and one last ball is put
in. What is the probability that this last ball is white?
我的想法是，這題等於是要求最後盒子裡剩下一黑一白的機率?
可是當這樣想時，感覺只有一步一步列舉的方法，不知道有沒有更好的想法呢？
謝謝大家!
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