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document.write( "We'll start out allowing 0 to be a first digit then we'll \r\n" );
document.write( "count those and subtract.\r\n" );
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document.write( "There are 5 positions for the 5 digits.\r\n" );
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document.write( "Choose the position for the 2 in 5 ways.\r\n" );
document.write( "Choose the position for the 5 in 4 ways.\r\n" );
document.write( "There are three vacant positions remaining.\r\n" );
document.write( "Choose a digit to go in the leftmost vacant position 6 ways.\r\n" );
document.write( "Choose a digit to go in the middle vacant position 5 ways.\r\n" );
document.write( "Choose a digit to go in the rightmost vacant position 4 ways.\r\n" );
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document.write( "That's (5)(4)(6)(5)(4) = 2400\r\n" );
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document.write( "We must now count the undesired ones, i.e., that begin with 0. \r\n" );
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document.write( "We can consider these to be 4-digit numbers with digits from\r\n" );
document.write( "{1, 2, 3, 4, 5, 6, 7} that must include the digits 2 and 5.\r\n" );
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document.write( "There are 4 positions for the 4 digits.\r\n" );
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document.write( "Choose the position for the 2 in 4 ways.\r\n" );
document.write( "Choose the position for the 5 in 3 ways.\r\n" );
document.write( "There are two vacant positions remaining.\r\n" );
document.write( "Choose a digit to go in the leftmost vacant position 5 ways.\r\n" );
document.write( "Choose a digit to go in the rightmost vacant position 4 ways.\r\n" );
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document.write( "That's (4)(3)(5)(4) = 240\r\n" );
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document.write( "Subtracting, 2400-240 = 2160 <--ANSWER\r\n" );
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document.write( "Edwin \n" );
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