Is it proportional: x 2, 4, 5; y 3, 6, 7.5

Step by step

The question

Question: is this table proportional: x is 2, 4, 5, and y is 3, 6, 7.5?

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.

3/2 is 1.5.

6/4 is 1.5.

7.5/5 is 1.5.

2 Compare the answers

The same number every time.

So it is proportional, and k = 1.5.

3 Write the equation

y = k x, with k = 1.5.

So the equation is y = 1.5x.

4 Check

Let's check: k times x should give each y.

1.5 times 2 is 3.

1.5 times 4 is 6.

1.5 times 5 is 7.5.

So the answer is right!

Let's look back.

First: divide y by x.

Then: compare the answers.

Then: write the equation.

Last: check.