# Thread: Setting up an Equation and solving....

1. ## Setting up an Equation and solving....

I need to reverse a formula that was given to me in an equation.

The problem is..
For the following function, C computes the cost in millions of dollars of implementing a city recycling project when x percent of the citizens participate.

The formula is

C(x) = 1.5x
100 - x

I solved that...... now it says...

Using this model, estimate the percentage of participation that can be excepted if \$5 million is spent on this recycling project? Set up an equation and solve algebraically. Round to the nearest whole percent.

I have no clue how to turn the equation around.

It's been 25 years since I took algebra in highschool and I'm expected to regurgitate it for College Algebra... can anyone atleast help me with setting up the formula?

2. If
C(x) = 1.5x / (100 -x)
then
what is x when C(x) = 5?

That is what the problem ask you.

5 = 1.5x / (100 -x)
Clear the fraction, multiply both sides by (100 -x),
5(100 -x) = 1.5x

500 -5x = 1.5x
500 = 1.5x +5x
500 = 6.5x
x = 500/6.5 = 76.923 percent

That is 77 percent of the population participating. ---answer.

3. OMG....

I would never have guessed to do that...

Thanks so much!!!