document.write( "Question 102945: By weight, a 200 ton sample of a certain roadbed material is 75% crushed rock. How many tons of a 30% crushed rock sample must be added to create a mixture that is 50% crushed rock?
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Algebra.Com's Answer #74869 by Earlsdon(6294)\"\" \"About 
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Let x = the number of tons of 30% crushed required.
\n" ); document.write( "To start with, you have 200 tons of 75% crushed rock to which you will add x tons of 30% crushed rock to obtain (200+x) tons of 50% crushed rock.
\n" ); document.write( "Now you can write the necessary equation to solve for x.
\n" ); document.write( "Change the percentages to their decimal equivalents. (75% = 0.75, 30% = 0.3, and 50% = 0.5)
\n" ); document.write( "200(0.75)+x(0.3) = (200+x)(0.5) Simplify and solve for x.
\n" ); document.write( "150+0.3x = 100+0.5x Subtract 0.3x from both sides to combine like-terms.
\n" ); document.write( "150 = 100+0.2x Now subtract 100 from both sides.
\n" ); document.write( "50 = 0.2x Finally, divide both sides by 0.2
\n" ); document.write( "250 = x
\n" ); document.write( "You will need to add 250 tons of 30% crushed rock to obtain 450 tons of 50% crushed rock.
\n" ); document.write( "Check:
\n" ); document.write( "200(0.75)+250(0.3) = 450(0.5)
\n" ); document.write( "150+75 = 225
\n" ); document.write( "225 = 225 OK!
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