document.write( "Question 619064: John bought a number of notepads for $70. Four of the notepads got spoiled. He sold the remaining notepads at $3 more per pad than he paid, and made a total profit of $10. How many notepads did John buy? \n" ); document.write( "

Algebra.Com's Answer #389326 by ankor@dixie-net.com(22740) $\"\"$ $\"About$

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John bought a number of notepads for $70.
\n" ); document.write( " Four of the notepads got spoiled.
\n" ); document.write( " He sold the remaining notepads at $3 more per pad than he paid, and made a total profit of $10.
\n" ); document.write( " How many notepads did John buy?
\n" ); document.write( ":
\n" ); document.write( "Let n = number of pads he bought
\n" ); document.write( "then
\n" ); document.write( "(n-4) = number of pads sold
\n" ); document.write( ":
\n" ); document.write( " $\"70%2Fn\"$ = original cost for each pad
\n" ); document.write( ":
\n" ); document.write( " $\"70%2Fn\"$ + 3 = selling price of the each pad
\n" ); document.write( ":
\n" ); document.write( "Revenue - cost = $10
\n" ); document.write( "(n-4)*( $\"70%2Fn\"$ + 3) - 70 = 10
\n" ); document.write( "(n-4)*( $\"70%2Fn\"$ + 3) = 80
\n" ); document.write( " $\"%2870%28n-4%29%29%2Fn\"$ + 3(n-4) = 80
\n" ); document.write( " $\"%2870n-280%29%2Fn\"$ + 3n - 12 = 80
\n" ); document.write( " $\"%2870n-280%29%2Fn\"$ + 3n = 92
\n" ); document.write( "multiply by n
\n" ); document.write( "70n - 280 + 3n^2 = 92n
\n" ); document.write( "Arrange as a quadratic equation
\n" ); document.write( "3n^2 + 70n - 92n - 280 = 0
\n" ); document.write( "3n^2 - 22n - 280 = 0
\n" ); document.write( "you can use the quadratic formula, but this will factor to
\n" ); document.write( "(3n + 20)(n - 14) = 0
\n" ); document.write( "Positive solution
\n" ); document.write( "n = 14 note pads originally bought
\n" ); document.write( ":
\n" ); document.write( ":
\n" ); document.write( "See if that checks out
\n" ); document.write( "70/14 = $5 original cost
\n" ); document.write( "then
\n" ); document.write( "5 + 3 = $8 selling price
\n" ); document.write( ":
\n" ); document.write( "10* 8 = $80 revenue, (4 less sold)
\n" ); document.write( "cost: = $70
\n" ); document.write( "------------
\n" ); document.write( "profit: $10 \n" ); document.write( "

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