document.write( "Question 1091481: How many even three-digit numbers can be formed from the
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document.write( "digits: 0, 1, 2, 3, 4, 5, 6 such that 5 is never placed
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document.write( "in the tens position? \n" );
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Algebra.Com's Answer #706062 by Gentle Phill(18)![]() ![]() You can put this solution on YOUR website! #Soln \n" ); document.write( ". \n" ); document.write( "Given d digits: \n" ); document.write( "0,1,2,3,4,5,6 \n" ); document.write( ". \n" ); document.write( "To form even 3-digits without repitition & place of 50: \n" ); document.write( ". \n" ); document.write( "1. Nos must end with either 0,2,4,6 \n" ); document.write( ". \n" ); document.write( "2. Nos must not Bgin with 0 \n" ); document.write( ". \n" ); document.write( "3. By given rule, 5 must not appear in the middle \n" ); document.write( ". \n" ); document.write( "To ensure coverage for all of the above without contradiction, we must observe D many cases possible bit by bit \n" ); document.write( ". \n" ); document.write( "#Case_1: 0 as unit \n" ); document.write( ". \n" ); document.write( "When 0 is unit, any no. can occupy 1st spot: \n" ); document.write( "1_0 \n" ); document.write( "2_0 \n" ); document.write( "3_0 \n" ); document.write( "4_0 \n" ); document.write( "5_0 \n" ); document.write( "6_0 \n" ); document.write( ". \n" ); document.write( "However: \n" ); document.write( ". \n" ); document.write( "~ When 1,2,3,4 nd 6 re 1st digit, 5 is neva used. We'll've: \n" ); document.write( ". \n" ); document.write( "[5][4][1] = 20 \n" ); document.write( ". \n" ); document.write( "Since 0 takes last spot, 1 of 5 nos takes 1st spot and 1 of d remainin 4 nos take 2nd spot \n" ); document.write( ". \n" ); document.write( "~ When 5 occupies 1st spot, we'll've: \n" ); document.write( ". \n" ); document.write( "[1][5][1] = 5 \n" ); document.write( ". \n" ); document.write( "#Case_2: Either of 2,4,6 as unit \n" ); document.write( ". \n" ); document.write( "Digit could start with 1,3,5 & any other 2 even not used as unit \n" ); document.write( ". \n" ); document.write( "However: \n" ); document.write( ". \n" ); document.write( "~ When 5 isn't 1st digit, it isn't used at all: \n" ); document.write( ". \n" ); document.write( "[4][4][3] = 48 \n" ); document.write( ". \n" ); document.write( "i.e \n" ); document.write( "[1,3 or any 2 even not used up][remaining 4 nos excluding '5'][2,4 or 6] \n" ); document.write( ". \n" ); document.write( "~ When 5 is used: \n" ); document.write( ". \n" ); document.write( "[1][5][3] = 15 \n" ); document.write( ". \n" ); document.write( "i.e \n" ); document.write( "[only 5][any other 5 excluding used up evens][2,4,6] \n" ); document.write( ". \n" ); document.write( "Total = 20+5+48+15 = 88 \n" ); document.write( ". \n" ); document.write( ". \n" ); document.write( ". \n" ); document.write( "Your friend, \n" ); document.write( "Francis. \n" ); document.write( " |