document.write( "Question 291405: In an office building, a room contains 90 chairs. The number of chairs per row is three less than three times the number of rows. Find the number of rows and the number of chairs per row.
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Algebra.Com's Answer #210759 by ankor@dixie-net.com(22740)\"\" \"About 
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In an office building, a room contains 90 chairs.
\n" ); document.write( " The number of chairs per row is three less than three times the number of rows.
\n" ); document.write( " Find the number of rows and the number of chairs per row.
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\n" ); document.write( "Let r = no. of rows
\n" ); document.write( "Let n = no. of chair/row
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\n" ); document.write( "r * n = 90
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\n" ); document.write( "\"The number of chairs per row is three less than three times the number of rows.\"
\n" ); document.write( "n = 3r - 3
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\n" ); document.write( "Replace n in the equation: r*n = 90
\n" ); document.write( "r*(3r-3) = 90
\n" ); document.write( "3r^2 - 3r = 90
\n" ); document.write( "3r^2 - 3r - 90 = 0
\n" ); document.write( "simplify, divide by 3
\n" ); document.write( "r^2 - r - 30
\n" ); document.write( "Factor
\n" ); document.write( "(r-6)(r+5) = 0
\n" ); document.write( "positive solution
\n" ); document.write( "r = 6 rows
\n" ); document.write( "then
\n" ); document.write( "n = 3(6) - 3
\n" ); document.write( "n = 15 chairs in each row
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\n" ); document.write( "Check: 15 * 6 = 90 \n" ); document.write( "
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