Let's define variables:
x: number of times the ticket price increases ($ 1).
The income is given by:
I(x) = (15 + x)(500-20x)
We can rewrite this function in the following way:
I (x) = - 20x ^ 2 + 200x + 7500
We use the following equation to find the maximum:
max = (-b)/(2a)
where:
then, we have:
max = (-200)/(2(-20))
max = (200)/(40)
max=5
Thus, the ticket price that maximizes the benefit is:
15 + x = 15 + 5 = 20 $
Answer:
A ticket price that will maximize the charity's profit, if there are total 500 seats in the concert hall is:
$ 20