document.write( "Question 1085633: A fundraising company charges $200 plate for a local charity and sells 300 tickets. For every $10 increase they will lose 5 ticket sales. What would they charge to make a maximum profit and what is the profit? \n" ); document.write( "
Algebra.Com's Answer #699721 by josmiceli(19441)\"\" \"About 
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Let \"+n+\" = the number of $10
\n" ); document.write( "increases in the ticket price
\n" ); document.write( "Let \"+P+\" = the profit
\n" ); document.write( "------------------------------
\n" ); document.write( "[ profit ] = [ tickets sold ] x [ income from selling 1 ticket ]
\n" ); document.write( "\"+P+=+%28+300+-+5n+%29%2A%28+200+%2B+10n+%29+\"
\n" ); document.write( "\"+P+=+60000+-+1000n+%2B+3000n+-+50n%5E2+\"
\n" ); document.write( "\"+P+=+-50n%5E2+%2B+2000n+%2B+60000+\"
\n" ); document.write( "\"+P+=+-n%5E2+%2B+40n+%2B+1200+\"
\n" ); document.write( "----------------------------
\n" ); document.write( "This is a parabola with a maximum. Use the formula for
\n" ); document.write( "the ( n, P ) of the vertex ( maximum in this case )
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\n" ); document.write( "\"+n%5Bmax%5D+=+-b%2F%282a%29+\" where
\n" ); document.write( "\"+a+=+-1+\"
\n" ); document.write( "\"+b+=+40+\"
\n" ); document.write( "\"+n%5Bmax%5D+=+-40%2F%282%2A%28-1%29%29+\"
\n" ); document.write( "\"+n%5Bmax%5D+=+20+\"
\n" ); document.write( "So, for a maximum profit, they would charge:
\n" ); document.write( "\"+200+%2B+10n+=+200+%2B+10%2A20+\"
\n" ); document.write( "\"+200+%2B+10n+=+400+\"
\n" ); document.write( "$400 / plate
\n" ); document.write( "-------------------------------
\n" ); document.write( "To find the profit, \"+P+\", plug the value for \"+n+\"
\n" ); document.write( "back into the equation:
\n" ); document.write( "\"+P+=+-n%5E2+%2B+40n+%2B+1200+\"
\n" ); document.write( "\"+P%5Bmax%5D+=+-20%5E2+%2B+40%2A20+%2B+1200+\"
\n" ); document.write( "\"+P%5Bmax%5D+=+-400+%2B+800+%2B+1200+\"
\n" ); document.write( "\"+P%5Bmax%5D+=+1600+\"
\n" ); document.write( "The maximum profit is $1600
\n" ); document.write( "-----------------------------
\n" ); document.write( "Feel free to get a 2nd opinion if needed
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