Adding and subtracting negatives

Hello, and welcome to Myriora Maths! What is two, add negative five? And what is five, take away negative two? It sounds tricky, but a number line makes it easy. Let's walk!

On a number line, adding means walking to the right. Three add four: start at three, walk four steps right, and you're at seven. Taking away means walking to the left. Three take away five: walk five steps left, past zero, to negative two.

Now, what does adding a negative mean? Adding negative five is like being given a debt of five pounds: you end up with less. So adding a negative walks to the left. Two add negative five is the same as two take away five: negative three.

And taking away a negative? Look at this pattern. Five take away two is three. Five take away one is four. Five take away zero is five. Each answer goes up by one. So five take away negative one is six, and five take away negative two is seven!

So here are the two rules. Adding a negative is the same as taking away. Taking away a negative is the same as adding. It's like taking a debt away from you: you're better off!

Let's try one together. What is negative one, take away negative four? Say it out loud!

Taking away a negative is the same as adding. So it's negative one, add four: walk four steps right, to three!

Here's a question that catches lots of people. What is four, take away negative three? Some people say one, because they just do four take away three. But taking away a negative means adding: four add three is seven!

Your turn! What is negative two, add negative three? Pick the right card. You've got twenty seconds, or pause the video. Go!

Time's up! Adding a negative is the same as taking away. So it's negative two, take away three: walk three steps left, from negative two to negative five.

Quick review. Adding walks right, and taking away walks left. Adding a negative is the same as taking away. Taking away a negative is the same as adding. And when you're stuck, draw a number line! See you next time!