Please help

The profit function for Wannamaker Trophies is P(x) = -0.3x2 + fx - m,  where f represents the design fee for a customer’s awards and m represents the monthly office rent.  Also, P represents the monthly profit in dollars of the small business where x is the number of awards designed in that month.

 

a)       If $60 is charged for a design fee, and the monthly studio rent is $1,500; write an equation for the profit, P, in terms of x.

 

          Typing hint:  Type x-squared as x^2

 

Answer: P(x) = -0.3x^2 + fx – m

Given: f = 60 and m = 1500.
Simply plug in these values into the equation above.

 

b)       How much is the profit when 50 award designs are sold in a month?

            Answer: If x= the # of awards designed per month, and there are 50 awards designed in 1 month, then for this particular set of circumstances, x=50.

            Show your work here: you just pug x=50 into the equation from part a) and solve for P(x).

         

 

c)      

         

            Answer: To find how many awards need to be designed for maximum profit (x) then all you need to do is use the 2ax = -b formula to solve for x.

 

            Show your work here: the extreme point expression, 2ax=-b

Is actually the formula for finding the x-coordinate of the vertex. If you

graph -0.3x^2 + 60x - 1500, you will find that it is a parabola that opens

down (umbrella shaped) so then you know that the vertex is going to be a

maximum. If it is a parabola that opens up (u shaped) then you know that it

is a minimum. (Parabolas that open downward have a negative a-value and

parabolas that open up have a positive a-value.

                            

 

d)       What is the maximum profit?

          Answer: 

          Show your work here:

 

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Answers

I hope my step-by-step guide will make this question easier to understand.

a) I start by just copying down the equation you gave me

P = - 0.3 x^2 + fx - m

now write 60 instead of f and write 1500 instead of m and you get

P = - 0.3 x^2 + 60x - 1500

That is all you have to do in the first part. Not too bad was it?

b) Now just write 50 instead of the number of awards x

and work out what P comes to.

This is just simple arithmetic so hopefully you will find it easy.

P = - 0.3 (50)^2 + 60(50) - 1500

P = - 0.3 (2500) + 3000 - 1500

P = - 750 + 1500 = 750

That means the profit is $750

c) The graph of a quadratic function is a parabola.

If that function is

ax^2 + bx + c

we are told it will have a maximum or a minimum when

2ax = -b or x = -b/2a

(You are not asked to explain why)

In this example b = 60, a = - 0.3

The minus before the 0.3 should tell you that the parabola is "upside down".

So it will have a maximum when x = -b/2a = (-60)/(-0.3) = 100

In words, the profit is a maximum when the number of awards, x, is 100.

d) Working out this part is just like b) but we write 100, (rather than 50), for x.

P = - 0.3 (100)^2 + 60(100) - 1500 = 7500

As always the method is far more important than the answer to an individual question.

So when you have copied it all out,

may I suggest that you cover the answers up,

and try to work it out again on your own.

Regards - Ian

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