document.write( "Question 995434: A silversmith wishes to obtain an alloy containing at least 72% silver and at most 75% silver. Determine the greatest and least amounts of an 80% silver alloy that should be combined with a 65% silver alloy in order to have 30grams of the required alloy. \n" ); document.write( "
Algebra.Com's Answer #614224 by josmiceli(19441)\"\" \"About 
You can put this solution on YOUR website!
This is 2 problems in 1
\n" ); document.write( "Let \"+a+\" = grams of 80% alloy needed
\n" ); document.write( "Let \"+b+\" = grams of 65% alloy needed
\n" ); document.write( "---------------------------------
\n" ); document.write( "First solve for 72% silver end result
\n" ); document.write( "(1) \"+a+%2B+b+=+30+\"
\n" ); document.write( "(2) \"+%28+.8a+%2B+.65b+%29+%2F+30+=+.72+\"
\n" ); document.write( "-----------------------------
\n" ); document.write( "(2) \"+.8a+%2B+.65b+=+.72%2A30+\"
\n" ); document.write( "(2) \"+.8a+%2B+.65b+=+21.6+\"
\n" ); document.write( "(2) \"+80a+%2B+65b+=+2160+\"
\n" ); document.write( "(2) \"+16a+%2B+13b+=+432+\"
\n" ); document.write( "-----------------------
\n" ); document.write( "Multiply both sides of (1) by \"+13+\"
\n" ); document.write( "and subtract (1) from (2)
\n" ); document.write( "(2) \"+16a+%2B+13b+=+432+\"
\n" ); document.write( "(1) \"+-13a+-+13b+=+-390+\"
\n" ); document.write( "-----------------------
\n" ); document.write( "\"+3a+=+42+\"
\n" ); document.write( "\"+a+=+14+\"
\n" ); document.write( "and
\n" ); document.write( "(1) \"+14+%2B+b+=+30+\"
\n" ); document.write( "(1) \"+b+=+16+\"
\n" ); document.write( "-----------------------
\n" ); document.write( "-----------------------
\n" ); document.write( "Now solve for 75% alloy end result
\n" ); document.write( "(1) \"+a+%2B+b+=+30+\"
\n" ); document.write( "(2) \"+%28+.8a+%2B+.65b+%29+%2F+30+=+.72+\"
\n" ); document.write( "-----------------------------
\n" ); document.write( "(2) \"+.8a+%2B+.65b+=+.75%2A30+\"
\n" ); document.write( "(2) \"+.8a+%2B+.65b+=+22.5+\"
\n" ); document.write( "(2) \"+80a+%2B+65b+=+2250+\"
\n" ); document.write( "(2) \"+16a+%2B+13b+=+450+\"
\n" ); document.write( "------------------------
\n" ); document.write( "Multiply both sides of (1) by \"+13+\"
\n" ); document.write( "and subtract (1) from (2)
\n" ); document.write( "(2) \"+16a+%2B+13b+=+450+\"
\n" ); document.write( "(1) \"+-13a+-+13b+=+-390+\"
\n" ); document.write( "------------------------
\n" ); document.write( "\"+3a+=+60+\"
\n" ); document.write( "\"+a+=+20+\"
\n" ); document.write( "and
\n" ); document.write( "(1) \"+20+%2B+b+=+30+\"
\n" ); document.write( "(1) \"+b+=+10+\"
\n" ); document.write( "------------------
\n" ); document.write( "From these results,
\n" ); document.write( "the least amount of 80% alloy needed is 14 grams ( making 72% silver )
\n" ); document.write( "the most amount of 80% alloy needed is 20 grams ( making 75% silver )
\n" ); document.write( "-------------------
\n" ); document.write( "You can check the answers by plugging
\n" ); document.write( "\"+a+\" and \"+b+\" back into (2) for both
\n" ); document.write( "72% and 75% cases
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