document.write( "Question 1081901: find how many no between 5000 and 6000 can be formed from the digits 1,2,3,4,5,6
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document.write( "a) if no digits are repeated
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document.write( "b) if repeated digits are allowed \n" );
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Algebra.Com's Answer #695937 by jim_thompson5910(35256)![]() ![]() ![]() You can put this solution on YOUR website! Part (a)\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "The number must be between 5000 and 6000 so the number must start with 5. Any other starting point and we're not between 5000 and 6000. \r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "If we pull out the digit '5', we're left with 5 other choices: 1,2,3,4,6\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "Imagine that the four digit number is composed of 4 slots A through D. The first slot A is locked in at 5. The other 3 slots (slot B,C,D) can change. \r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "Slot B has 5 choices \n" ); document.write( "Once we make a choice, we have 4 choices left for slot C \n" ); document.write( "Slot D will have 3 choices\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "Overall, there are 5*4*3 = 60 different permutations when it comes to picking 3 items from a set of 5. \r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "The answer to part (a) is 60\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "-------------------------------------------------------------\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "Part (b)\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "Repeats are allowed now so we can reuse the digit '5' if we want to. There are still 3 slots to fill since the first slot is locked to be 5 (see explanation above).\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "The slots that aren't locked up (B through D) each have 6 choices giving 6*6*6 = 6^3 = 216 different three-digit combinations\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "So there are 216 different numbers we can form that are between 5000 and 6000.\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "The answer to part (b) is 216 \n" ); document.write( " |