Question

There are 17 brown ties,13 red ties, 9 green ties, 5 blue ties and 2 white ties.Then a man takes a tie. So, how many times he at least take tie to get the 2 ties in same colour?

Answer 1

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Assume no replacement: 
P(1 blue and 1 other colour) = 8/18 * 10/17 = 40/153 
P(1 blue and 1 blue) = 8/18 * 7/17 = 28/153 

40/153 + 28/153 = 4/9 is the probability at least one is blue



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