Lesson video

Hi, I'm Miss Davis.

In this lesson, we're going to be changing the subject of a formula.

The subject of a formula is the singular variable that is on one side of the equal sign.

Let's have a look at a few examples.

In this formula, y is the subject as it is on its own on one side of the equal symbol.

In this next example, p is the subject.

In our final example, s is the subject.

In this example, we've been asked to make x the subject of the formula This means we need to be left with x on its own on one side of the equal symbol.

To do that, we need to remove that p The left hand side of the equation says p add x, the inverse of adding p is subtracting P.

Let's subtract p from both sides.

This leaves us with x equals y, subtract p.

x is on its own on one side of the equal symbol.

So we have successfully changed the subject of the formula.

Let's look at this next example.

This next example says x divided by 5 is equal to y The inverse of dividing by 5 is multiplying by 5.

Let's multiply both sides by 5.

This gives us x is equal to 5y as 5y means 5 multiplied by y.

In this next example, we have again been asked to make x the subject of the formula.

Let's start by leaving just 4x.

On the left hand side of the equal symbol.

The inverse of adding 6 is subtracting 6.

If we subtract 6 from both sides, this leaves us with 4x is equal to y subtract 6.

4x means 4 multiplied by x the inverse of multiplying by 4 is dividing by 4.

If we divide both sides by 4, it gives us x equals y subtract 6 all divided by 4.

Our next example, is r subtract x is equal to y.

We need to make our x positive.

To do this, we're going to add x to both sides.

This gives us r is equal to y add x, we can then subtract y from both sides.

This gives an answer of r subtract y is equal to x.

Here are some questions for you to try Pause the video to complete your task and resume once you're finished.

Here are the answers in part e and f, make sure that you've made positive p the subject, not negative p.

Here is a question for you to try.

Pause the video to complete your task and resume once you're finished.

Here is the answer.

The first thing you needed to do was divide both sides by 3.

This gives x over 3 equals t subtract 5 and then add 5 to both sides.

This gives an answer of t equals x over 3 add 3 Here is a question for you to try.

Pause the video to complete your task.

And resume once you have finished Here is the answer.

John hasn't multiplied all of the terms by negative 2.

The correct answer is h is equal to negative 2g subtract 10.

That's all for this lesson.

Thanks for watching.