Question

Write a function rule to describe the amount of change c(x) from a $20 bill if you buy x pounds of grapes at $41.29 per pound.

Answer 1

`r(x) = 20 -1.29 x`

Explanation:

Let's define some notation first:

`x` represent the number of grapges that we buy

`A= 20` represent the amount of money that we have in order to pay

`C= 1.29` represent the unitary cost per each pound of grapes. This value sia assumed because is not logic that a pound of grapes cost $41.29.

`r` represent the change

Solution to the problem

In order to find a function to the change we need to satisfy the following equation:

`r+ Cx =A`

Because the change plus the ocost needs to be equal to the total amount.

If we solve for the change r we got this function:

`r = A- Cx`

And if we replace the values for A and C we got:

`r(x) = 20 -1.29 x`

And this would be our function for the change based on the info provided.