Question

Solve the problems.

1 Martin has an 18-cup container of flour that he uses for
muffins only. He uses 3 cups of the flour for every batch
of muffins he makes. Write an equation to show how
much flour is left in the container after x batches of
muffins. Then graph the function.
Show your work.

Answer 1

`y=-3x+18`

Explanation:

Let the amount of flour left be
`y`.

Initial amount of flour = 18 cups

Cups used for 1 batch of muffins = 3

∴ Cups used for
`x` batches =
`3* x=3x`

Amount left in the container is given as:

`y= \textrm{Initial amount - Amount used for x batches}\\y=18-3x\\y=-3x+18`

Therefore, the equation to show how much flour is left in the container after x batches of muffins is
`y=-3x+18`.

The graph of it is shown below.

Find the x and y intercepts and then join the line.

At x intercept,
`y = 0`

`0=-3x+18\\3x=18\\x=6`

So, x intercept is
`(6,0)`

At y intercept,
`x = 0`,

`y=-3(0)+18\\y=18`

So, y intercept is
`(0,18)`

Join these two points to plot the graph.