document.write( "Question 1151170: 2. If the permutation of the word WHITE is selected at random, how many of the
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document.write( "permutations
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document.write( "i. Begins with a consonant?
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document.write( "ii. Ends with a vowel?
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document.write( "iii. Has a consonant and vowels alternating? \n" );
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Algebra.Com's Answer #772819 by jim_thompson5910(35256) ![]() You can put this solution on YOUR website! \n" ); document.write( "i. \n" ); document.write( "Consonants to choose from = {W, H, T} \n" ); document.write( "Vowels to choose from = {I, E}\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "We have 3 consonants to fill slot 1. \n" ); document.write( "Then we have 4 choices for slot 2 \n" ); document.write( "Then 3 choices for slot 3 \n" ); document.write( "2 choices for slot 4 \n" ); document.write( "1 choice for slot 5\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "Overall, 3*4*3*2*1 = 3*4! = 3*24 = 72\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "There are 72 permutations that begin with a consonant.\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "Answer: 72\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "============================================ \n" ); document.write( "ii.\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "Slot 5 has 2 choices, either an E or an I. \n" ); document.write( "After slot 5 is filled, we have 4 choices for slot 1 \n" ); document.write( "Then 3 choices for slot 2 \n" ); document.write( "2 choices for slot 3 \n" ); document.write( "1 choice for slot 4\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "2*4*3*2*1 = 2*4! = 2*24 = 48\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "There are 48 permutations that have a vowel as the last letter.\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "Answer: 48\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "============================================ \n" ); document.write( "iii.\r \n" ); document.write( "\n" ); document.write( "define two variable placeholders \n" ); document.write( "c = consonant from the list {W, H, T} \n" ); document.write( "V = vowel from the list {I, E}\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "We want the consonants c and the vowels V to alternate. If we start with a consonant, then we must have a vowel next, and then another consonant, etc etc.\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "That pattern would be \n" ); document.write( "cVcVc\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "We can't start with a vowel because we'd have \n" ); document.write( "VcVcc \n" ); document.write( "we run out of vowels once we reach slot 3.\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "And of course we can't have something like this \n" ); document.write( "ccVcV \n" ); document.write( "because of the adjacent consonants in slots 1 and 2.\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "So again we only have something of the form \n" ); document.write( "cVcVc\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "Consider just the consonants for now. We basically have 3 slots to fill and 3 items to fill them. There are 3! = 3*2*1 = 6 ways to do this. Order matters.\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "Then we have 2 other slots for the vowels, so 2! = 2*1 = 2 ways to fill the vowel slots. \r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "Overall, there are 6*2 = 12 ways to have a permutation of letters such that the consonants and vowels alternate.\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "Answer: 12 \n" ); document.write( " \n" ); document.write( " \n" ); document.write( " |