Is it proportional: x 1, 2, 4; y 2, 3, 5

Step by step

The question

Question: is this table proportional: x is 1, 2, 4, and y is 2, 3, 5?

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.

2/1 is 2.

3/2 is 1.5.

5/4 is 1.25.

2 Compare the answers

The answers are not the same.

So it is not proportional.

Careful!

y goes up by the same amount each time.

But that is not enough.

y divided by x must stay the same.

3 Check

Let's check on a graph.

We put the points on the grid.

A straight line, but it does not go through (0, 0).

It misses (0, 0).

So the answer is right!

Let's look back.

First: divide y by x.

Then: compare the answers.

Last: check.