Question 491674: Suppose you are moving, and have 9 boxes. For this problem, order is not important.
i) find the number of ways of selecting 4 boxes out of 9.
ii) Suppose one box has your wallet. Find the number of ways of selecting 4 boxes, so that the box with your wallet is one of the four. (Hint: how many ways of getting 3 more boxes out of the remaining 8 are there?)
iii) If you select 4 boxes at random, find the probability that your wallet will be in one of these four. Use the results from parts i and ii to answer this problem.
Answer by stanbon(75887)   (Show Source):
You can put this solution on YOUR website! Suppose you are moving, and have 9 boxes. For this problem, order is not important.
i) find the number of ways of selecting 4 boxes out of 9.
Ans: 9C4 = (9*8*7*6)/(1*2*3*4) = 126
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ii) Suppose one box has your wallet. Find the number of ways of selecting 4 boxes, so that the box with your wallet is one of the four. (Hint: how many ways of getting 3 more boxes out of the remaining 8 are there?)
Ans = 8C3 = 56
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iii) If you select 4 boxes at random, find the probability that your wallet will be in one of these four. Use the results from parts i and ii to answer this problem.
Ans = 1 - [56/126] = 1 - 0.4444 = 0.5556
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Cheers,
Stan H.
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