Question 1172626: formula for the probability of picking the same 2 items out of 10 5times in a row when the the items are rearranged each time and then how you answered the problem i need the formula and what numbers plug into it and where because I have multiple others to solve thank you
Answer by Boreal(15235)   (Show Source):
You can put this solution on YOUR website! This is 2/10*1/9 or 1/45; the probability of getting the first one right* the probability of getting the second right, given the first was right.
10C2 are the number of ways to choose 2 out of 10, and only 1 way is correct, so that is 1/45. May write as
2C2/10C2
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To do it 5 times in a row is (1/45)^5=5.4 x 10^(-9), because they are independent trials.
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