document.write( "Question 412390: 1.how many ways can 5 people occupy 8 chair if no two people are to occupy the same chair?\r
\n" ); document.write( "\n" ); document.write( "i do not understand why this question have to use permutation instead of combinations. >.<\"
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Algebra.Com's Answer #289661 by Theo(13342)\"\" \"About 
You can put this solution on YOUR website!
permutations assume that order is important.\r
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\n" ); document.write( "\n" ); document.write( "combinations assume that order is not important.\r
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\n" ); document.write( "\n" ); document.write( "you have a total of 8 chairs.\r
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\n" ); document.write( "\n" ); document.write( "5 people can occupy these chairs in P(8,5) = 8! / 3! = 6720 ways.\r
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\n" ); document.write( "\n" ); document.write( "That's a lot of ways.\r
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\n" ); document.write( "\n" ); document.write( "To make it simpler to see, let's assume there are 3 chairs and 2 people.\r
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\n" ); document.write( "\n" ); document.write( "In how many ways can those 2 people occupy 3 chairs.\r
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\n" ); document.write( "\n" ); document.write( "The answer should be 3! / 1! = 6 ways.\r
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\n" ); document.write( "\n" ); document.write( "Let's label the chairs a, b, and c.\r
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\n" ); document.write( "\n" ); document.write( "Now we draw the possible number of sets of 2 from 3 chairs.\r
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\n" ); document.write( "\n" ); document.write( "They would be:\r
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\n" ); document.write( "\n" ); document.write( "ab
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\n" ); document.write( "\n" ); document.write( "Notice that the 6 possible ways include sets that involve the same people, only in a different order.\r
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\n" ); document.write( "\n" ); document.write( "ab can be paired with ba
\n" ); document.write( "ac can be paired with ca
\n" ); document.write( "bc can be paired with cb\r
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\n" ); document.write( "\n" ); document.write( "If we were dealing with combinations, then the answer would be 3 possible ways because we only have 3 sets where the people involved in each set are different from the other sets.\r
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\n" ); document.write( "\n" ); document.write( "you would have:\r
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\n" ); document.write( "\n" ); document.write( "ab
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\n" ); document.write( "\n" ); document.write( "Order, in this case, would not be important, so you would have less possible sets.\r
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\n" ); document.write( "\n" ); document.write( "None of these sets have the same 2 people in them.\r
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\n" ); document.write( "\n" ); document.write( "Formula for permutations is n! / (n-x)!\r
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\n" ); document.write( "\n" ); document.write( "Formula for combinations is n! / ((n-x)! * x!)\r
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\n" ); document.write( "\n" ); document.write( "With permutations the answer is 3!/1! = 3*2*1/1 = 6\r
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\n" ); document.write( "\n" ); document.write( "With combinations the answer is 3!/(1!2!) = 3*2*1/1*2 = 3\r
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\n" ); document.write( "\n" ); document.write( "The answer is because, when you arrange people in chairs, order is important.\r
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\n" ); document.write( "\n" ); document.write( "If I did my math correctly, your answer should be 8! / 3! = 6720 possible ways.\r
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