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Zib
06-19-2011, 11:54 AM
Copies of Mr. McCallum's old quizzes sell for $10 each. At this price, 200 copies will be sold. An informal survey indicates that for each $1 that the price is increased, 10 less quizzes will be sold.
a) What price should the quizzes be sold for to maximize revenue? Answer: $15
b) If a revenue of $2160 is generated, what was the cost of a single copy? Answer: $12

This is what I tried to do:
Price: (10+x) Quantity: (200-10x)
Revenue=(10+x)(200-10x)
=10x^2-100x-2000
=10(x-5)^2-4250
Therefore a $5 price increase will maximize revenue.

Help would be much appreciated.

galactus
06-19-2011, 12:08 PM
You have it. They are initially $10. A $5 increase beings them to $15.

part b, (10+x)(200-10x)=2160

Solve for x.

Zib
06-19-2011, 12:09 PM
Thank you! I just couldn't figure out what I was doing wrong... :roll: