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標題:
Permutation
發問:
There are 3 red balls, 4 white balls and 5 black balls. From this group of balls, find the number of arrangements of " first ball white, second ball white, third ball any color and fourth ball red " (that is WWAR).
最佳解答:
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The number of combinations are White – white – non red – red and White – white – red – red = 4 * 3 * 6 * 3 + 4 * 3 * 3 * 2 = 324 2010-05-30 10:44:40 補充： Correction 4*3*7*3 + 4*3*3*2=324 2010-05-30 10:45:55 補充： Better to say the number of arrangements (rather than combinations)...
其他解答:4E350C6F06A145F0
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