document.write( "Question 1158401: Find how many distinct numbers greater than 5000 and divisible by 3 can be formed from the digits 3,4,5,6 and 0, if each digit is used atmost once in a number? \n" ); document.write( "
Algebra.Com's Answer #781436 by greenestamps(13200)![]() ![]() You can put this solution on YOUR website! \n" ); document.write( "Edwin's solution is good, as usual. \n" ); document.write( "Here is another approach, to show you there is almost always more than one way to analyze a problem. \n" ); document.write( "The sum of the five given digits is 18, which is divisible by 3. Since all 5-digit numbers are greater than 5000, every 5-digit number that can be formed with these digits satisfies the requirements. \n" ); document.write( "The first digit can't be 0; so we can choose... \n" ); document.write( "the first digit 4 ways; \n" ); document.write( "the second digit 4 ways; \n" ); document.write( "the third digit 3 ways; \n" ); document.write( "the fourth digit 2 ways; and \n" ); document.write( "the fifth digit 1 way. \n" ); document.write( "Number of 5-digit numbers we can make: 4*4*3*2*1 = 96. \n" ); document.write( "For 4-digit numbers, the first digit must be either 5 or 6 if the number is going to be greater than 5000. \n" ); document.write( "4-digit numbers with first digit 6.... \n" ); document.write( "With first digit 6, for the sum of the digits to be divisible by 3, the digits 4 and 5 must both be used. So we must use both of those digits and choose one of the remaining two digits; then those last three digits can be arranged in 3!=6 different ways. \n" ); document.write( "Number of 4-digit numbers with leading digit 6: 2*6 = 12. \n" ); document.write( "4-digit numbers with first digit 5.... \n" ); document.write( "With first digit 5, for the sum of the digits to be divisible by 3, the digit 4 must also be used. So we use the 4, and we choose 2 of the remaining 3 digits. We can choose 2 of the remaining three digits is C(3,2)=3 ways; then those last three digits can be arranged in 3!=6 different ways. \n" ); document.write( "Number of 4-digit numbers with leading digit 6: 3*6 = 18. \n" ); document.write( "Total number of numbers we can form: 96+12+18 = 126. \n" ); document.write( " \n" ); document.write( " |