document.write( "Question 267021: how many positive four –digits integers of the form _ _ 45 are divisible by 45 ? \n" ); document.write( "
Algebra.Com's Answer #196103 by Edwin McCravy(20060)\"\" \"About 
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document.write( "If a positive integer is divisible by 45 it must be divisible by\r\n" );
document.write( "both 9 and 5.  Since any integer of the form XY45 ends in 5 it \r\n" );
document.write( "is automatically divisible by 5. Therefore we only need to make \r\n" );
document.write( "sure the number is divisible by 9 as well.  A positive integer is\r\n" );
document.write( "divisible by 9 if and only if the sum of its digits is a multiple\r\n" );
document.write( "of 9.  Since the sum of the last two digits is a multiple of 9,\r\n" );
document.write( "the sum of the first two digits must also be a multiple of 9.  \r\n" );
document.write( "Therefore, the only possibilities are\r\n" );
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document.write( "1845, 2745, 3645, 4545, 5445, 6345, 7245, 8145, 9045, and 9945.\r\n" );
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document.write( "So there are exactly 10 such positive integers.\r\n" );
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document.write( "Edwin

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