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 #826489 by ikleyn(52797) $\"\"$ $\"About$

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document.write( "420 lbs of the 20% sand mixture contains 0.20*420 = 84 lbs of sand.\r\n" );
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document.write( "Hence,  420-84 = 336 lbs is another material (not sand): break stone and cement.\r\n" );
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document.write( "We want 336 lbs be 75% of the new mixture;  hence, the total new mixture is   = 448 lbs.\r\n" );
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document.write( "It means that  448-420 = 28 lbs of sand should be added.    ANSWER\r\n" );
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\n" ); document.write( "\n" ); document.write( "Solved mentally, without using equations (only calculator :)\r
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