document.write( "Question 1209361: How many values greater than 7000 can be formed using the digits 3, 5, 7, 8, 9 without repetition? \n" ); document.write( "
Algebra.Com's Answer #848677 by math_tutor2020(3817)![]() ![]() ![]() You can put this solution on YOUR website! \n" ); document.write( "Consider four-digit numbers of the form ABCD where A,B,C,D represent digits chosen from {3,5,7,8,9} with no repeats allowed. \n" ); document.write( "The choices for A could be 7, 8 or 9 to ensure that the number exceeds 7000. \n" ); document.write( "So we have 3 choices for slot A. \n" ); document.write( "Whatever is selected for A, we have 4 choices for B, 3 for C, and 2 for D. \n" ); document.write( "It yields 3*4*3*2 = 72 different ways to create the four-digit numbers.\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "Now consider the five-digit case. Numbers will look like ABCDE \n" ); document.write( "Where A through E are chosen from {3,5,7,8,9} and no repeats are allowed. \n" ); document.write( "There are 5*4*3*2*1 = 120 possible five-digit values larger than 7000. \n" ); document.write( "Any permutation of these 5 digits will be larger than 7000 simply because any five-digit number is larger than any four-digit number. \n" ); document.write( "We cannot form six-digit numbers or larger since we only have 5 digits to work with and repeats aren't allowed.\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "We found there are 72 ways to form the four-digit numbers, and 120 ways to form the five-digit numbers, such that whatever formed is larger than 7000.\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "Therefore, \n" ); document.write( "72+120 = 192 is the final answer. \n" ); document.write( " \n" ); document.write( " |