<PRE><B>Question 458926</B>
Suppose that customers will purchase q unit of a product when the price is (80-q)/4 dollars each,
how many units must be sold in order that sales revenue be $400?
:
Revenue = price * no. of units purchased
therefore
{{{(80-q)/4}}} * q = 400
:
{{{(80q - q^2)/4}}} = 400
Multiply both sides by 4
80q - q^2 = 1600
Combine on the right
0 = q^2 - 80q + 1600
this factors to
(q-40)(q-40) = 0
q = 40 units sold to have a revenue of $400
:
:
Check this out; find the price
p = {{{(80-40)/4}}}
p = $10
 40 * 10 = 400</PRE>