document.write( "Question 829757: A number is between 20 and 30 and is three times the sum of its digits. What is the number?
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Algebra.Com's Answer #500128 by MathTherapy(10552)\"\" \"About 
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\n" ); document.write( "A number is between 20 and 30 and is three times the sum of its digits. What is the number?
Let tens and units digits be T and U, respectively
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document.write( "Then number is: 10T + U
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document.write( "So, 20 < 10T + U < 30 ------- inequality (i)
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document.write( "Also, 10T + U = 3(T + U)____10T + U = 3T + 3U___7T = 2U___\"U+=+7T%2F2\" ----- inequality (ii)
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document.write( "20 < 10T + \"7T%2F2\"< 30 ------ Substituting \"7T%2F2\" for U in inequality(i) 
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document.write( "40 < 20T + 7T < 60 ----- Multiplying by LCD, 2
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document.write( "40 <    27T   < 60
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document.write( "\"40%2F27+%3C+T+%3C+60%2F27\" ------ Dividing by 27
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document.write( "\"1%2613%2F27+%3C+T+%3C+2%266%2F27\"\r
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document.write( "Since tens digit, or \"T+%3E+1%2613%2F27\", but \"T+%3C+2%266%2F27\", then T or tens digit MUST BE 2
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document.write( "U = 7(2)/2 ------- Substituting 2 for T in inequality (ii)
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document.write( "\"U+=+14%2F2\", or 7\r
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document.write( "With T being 2 and U being 7, number is: \"highlight_green%2827%29\"
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