document.write( "Question 178908: Suppose you have a lemonade stand, and when you charge $2 per cup of lemonade you sell 120 cups. But when you raise your price to $3 you only sell 60 cups. Write an equation for the number of cups you sell as a function of the price you charge. Denote \"C\" for number of cups, and \"P\" for the price you charge. Assume the function is linear.
\n" ); document.write( " \n" ); document.write( "
Algebra.Com's Answer #133867 by ankor@dixie-net.com(22740)\"\" \"About 
You can put this solution on YOUR website!
Suppose you have a lemonade stand, and when you charge $2 per cup of lemonade
\n" ); document.write( " you sell 120 cups. But when you raise your price to $3 you only sell 60 cups.
\n" ); document.write( " Write an equation for the number of cups you sell as a function of the price
\n" ); document.write( " you charge. Denote \"C\" for number of cups, and \"P\" for the price you charge.
\n" ); document.write( " Assume the function is linear.
\n" ); document.write( ":
\n" ); document.write( "Make coordinates from the given information
\n" ); document.write( "x1=2, y1=120
\n" ); document.write( "x2=3, y2=60
\n" ); document.write( ":
\n" ); document.write( "Find the slope (m), where m = \"%28y2-y1%29%2F%28x2-x1%29\":
\n" ); document.write( "m = \"%2860-120%29%2F%283-2%29\"
\n" ); document.write( "m = \"%28-60%29%2F1\" = -60
\n" ); document.write( ":
\n" ); document.write( "write the equation using the point/slope formula [y-y1 = m(x-x1)]
\n" ); document.write( "y - 120 = -60(x - 2)
\n" ); document.write( "y - 120 = -60x + 120
\n" ); document.write( "y = -60x +120 + 120
\n" ); document.write( "y = -60x + 240
\n" ); document.write( "Translate this to your problem where x=p, y=C
\n" ); document.write( "C(p) = -60p + 240
\n" ); document.write( ":
\n" ); document.write( ":
\n" ); document.write( "you can check this by substituting 2 for p and ensuring that C(p) = 120
\n" ); document.write( "do the same for p=3
\n" ); document.write( " \n" ); document.write( "
\n" );