# Thread: Grade 11 word problem? (Quadratic equations) #2

1. ## Grade 11 word problem? (Quadratic equations) #2

Lemon Motors has been selling an average of 60 new cars per month at $800 over the factory price. They are considering an increase in this markup. A marketing survey indicates that for every$20 increase, they will sell one less car each month. What should their new markup be to maximize income?

I know I have to complete the square to find the maximum, but I just can't think of an equation to describe the situation.

2. Originally Posted by Sorena
Lemon Motors has been selling an average of 60 new cars per month at $800 over the factory price. They are considering an increase in this markup. A marketing survey indicates that for every$20 increase, they will sell one less car each month. What should their new markup be to maximize income?

I know I have to complete the square to find the maximum, but I just can't think of an equation to describe the situation.
let x = number of $20 price increases ... monthly revenue = (number of cars sold)(price) R(x) = (60 - x)(800 + 20x) 3. the answer is 1000$ but i dont get that.

4. Originally Posted by Sorena
the answer is 1000$but i dont get that. I agree that the price of the car should be$1000 to maximize revenue.

what did you "get" and how did you arrive at that value?