document.write( "Question 726866: a fertilizer manufacturer has two fertilizers, one which contains 24% nitrogen, and the other contains 16% nitrogen. How much of each fertilizer should be mixed together to make 500 pounds of a fertilizer that is 21% nitrogen? \n" ); document.write( "
Algebra.Com's Answer #444873 by DrBeeee(684)\"\" \"About 
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Let x = lbs of 24% fertilizer
\n" ); document.write( "Let y = lbs of 16% fertilizer
\n" ); document.write( "Known:
\n" ); document.write( "1) x is 24% nitrogen
\n" ); document.write( "2) y is 16% nitrogen
\n" ); document.write( "3) Mixture is 21% nitrogen
\n" ); document.write( "4) total weight is 500lb
\n" ); document.write( "Equations:
\n" ); document.write( "(1) x + y = 500
\n" ); document.write( "(2) .24x + .16y = .21*500
\n" ); document.write( "Solve (1) for x and get
\n" ); document.write( "(3) x = 500 - y
\n" ); document.write( "Now substitute (3) into (2) to get
\n" ); document.write( "(4) .24*(500-y) + .16y = 105 or
\n" ); document.write( "(5) 120 - .24y + .16y = 105 or
\n" ); document.write( "(6) 0.08y = 15 or
\n" ); document.write( "(7) y = 15/0.08 or
\n" ); document.write( "(8) y = 187.5
\n" ); document.write( "From (3) we get
\n" ); document.write( "(9) x = 500 - 187.5 or
\n" ); document.write( "(10) x = 312.5
\n" ); document.write( "Let's check with (2).
\n" ); document.write( "Is (.24*312.5 + .16*187.5 = .21*500)?
\n" ); document.write( "Is (75 + 30 = 105)?
\n" ); document.write( "Is (105 = 105)? Yes
\n" ); document.write( "Answer:Mix 312.5lbs of 24% nitrogen fertilizer and 187.5lbs of 16% nitrogen fertilizer to get 500 lbs of 21% nitrogen fertilizer.\r
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