document.write( "Question 1194310: How much sand must be added to 420lbs of concretemix that is 20% sand to have a mix that is 25% sand \n" ); document.write( "

Algebra.Com's Answer #826477 by MathLover1(20850) $\"\"$ $\"About$

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Let $\"x\"$ lb of cement to be added
\n" ); document.write( "given:
\n" ); document.write( " $\"+.20%2A420lb=+84lb+\"$ of sand initially\r
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\n" ); document.write( "\n" ); document.write( " $\"+%28x+%2B+84%29+%2F+%28x+%2B+420%29+=+.25+\"$
\n" ); document.write( " $\"+x+%2B+84+=+.25%2A%28x+%2B+420%29+\"$
\n" ); document.write( " $\"+x+%2B+84+=+0.25+x+%2B+105+\"$
\n" ); document.write( " $\"+x-.25x+=+105-84+\"$
\n" ); document.write( " $\"+.75x+=+21+\"$
\n" ); document.write( " $\"+x+=+21%2F.75+\"$
\n" ); document.write( " $\"+x+=+28+\"$
\n" ); document.write( " $\"28lb\"$ of sand must be added\r
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\n" ); document.write( "\n" ); document.write( "check:\r
\n" ); document.write( "\n" ); document.write( " $\"+%2828%2B+84%29+%2F+%2828+%2B+420%29+=+.25+\"$
\n" ); document.write( " $\"+112+%2F+448+=+.25+\"$
\n" ); document.write( " $\"+.25+=+.25+\"$ \r
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