Is it proportional: x 1, 2, 3; y 4, 8, 12

Step by step

The question

Question: is this table proportional: x is 1, 2, 3, and y is 4, 8, 12?

Proportional means: y divided by x is always the same number.

We call that number k.

Then y = k times x.

We write it as a table.

1 Divide y by x

For each pair we work out y divided by x.

4/1 is 4.

8/2 is 4.

12/3 is 4.

2 Compare the answers

The same number every time.

So it is proportional, and k = 4.

3 Write the equation

y = k x, with k = 4.

So the equation is y = 4x.

4 Check

Let's check on a graph.

We put the points on the grid.

They lie on a straight line through (0, 0).

That is the picture of proportional.

So the answer is right!

Let's look back.

First: divide y by x.

Then: compare the answers.

Then: write the equation.

Last: check.