.
An equivalent rephrasing is "for each decrease the price in 1 cent the number of sold hot dogs increases in 1", or
in the Math term, at the price 200-n cents the number of sold hot dogs is 100+n.
Then the revenue is R(n) = (100+n)*(200-n) = 20000 + 200n - 100n - n^2 = -n^2 + 100n + 20000.
And the problem asks to find the maximum of the quadratic form R(n).
The maximum is achieved at n = = 50.
Anser. The food truck should charge 200-50 = 150 cents = $1.50 per hot dog.
My lessons in this site on finding the maximum/minimum of a quadratic function are
- HOW TO complete the square to find the minimum/maximum of a quadratic function
- Briefly on finding the minimum/maximum of a quadratic function
- HOW TO complete the square to find the vertex of a parabola
- Briefly on finding the vertex of a parabola
- OVERVIEW of lessons on finding the maximum/minimum of a quadratic function
Also, you have this free of charge online textbook in ALGEBRA-I in this site
- ALGEBRA-I - YOUR ONLINE TEXTBOOK.
The referred lessons are the part of this textbook under the topic "Finding minimum/maximum of quadratic functions".
Save the link to this online textbook together with its description
Free of charge online textbook in ALGEBRA-I
https://www.algebra.com/algebra/homework/quadratic/lessons/ALGEBRA-I-YOUR-ONLINE-TEXTBOOK.lesson
to your archive and use it when it is needed.