document.write( "Question 1026955: A six digit number is to be formed using only digits from the set {1,2,3,5,6,7,9}. There are to be three distinct digits in the numbers formed, one of which appears four times and the other two, once each. How many different numbers are possible. \n" ); document.write( "
Algebra.Com's Answer #642233 by richard1234(7193)![]() ![]() You can put this solution on YOUR website! Choose the digit that appears four times (7 ways), then choose the remaining two digits (say A and B). Assume that A and B are chosen with order important (6*5 = 30 ways) - you will see why later.\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "Choose four of the six placeholders for the digit that appears four times to occupy (6C4 = 15 ways). Then put A (the first of the 2 digits chosen) in the first unoccupied spot and B in the second unoccupied spot. This constructs such a number, and we know that we didn't overcount.\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "# of ways = 7*30*15 = 3150\r \n" ); document.write( "\n" ); document.write( " \n" ); document.write( " |