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# Maths Years F–1 with Miss James: Subtraction using a number line

**Subjects: Maths **

**Years: F–2**

### Learn the "counting back" strategy to help you solve tricky subtraction problems.

In this lesson, Miss James demonstrates how to use a number line correctly, and she provides opportunities for you to have a go at home.

**Things to think about **

For this lesson you will need: 1 pencil, 1 piece of paper. Can you say what number comes before:

Special vocabulary used in this lesson: Subtraction, Number line, Counting-back strategy.

- Think about the different words that are used to mean "subtract" or "subtraction". Think about which way you should move along the number line to subtract a number. Count along with Miss James as she counts backwards on her number line. Write the equations Miss James writes on your piece of paper. Draw a number line from 1 to 10 on your piece of paper.

Get a deck of cards to practice the counting-back strategy. Draw two cards from the deck and subtract the two numbers of the cards using a number line. Remember to use the biggest number first! Download

**this worksheet**to help you with the counting back strategy.

**Acknowledgements**

Special thanks to Miss James and Haileybury, Melbourne.

**Production Date: **2020

**Copyright**

^{Metadata © Australian Broadcasting Corporation 2020 (except where otherwise indicated). }^{Digital content © Australian Broadcasting Corporation (except where otherwise indicated). }^{Video © Australian Broadcasting Corporation and Department of Education and Training (Victoria). All images copyright their respective owners. }^{Text © Australian Broadcasting Corporation and Department of Education and Training (Victoria).}

## Transcript

Hi, my name is Miss James and I can't wait to find out just how clever you are in our lesson today.

For this lesson all you will need is a pencil and a piece of paper. In this game, you need to tell me how many fingers I'm holding up. Great job! I had five. You've got to be quick. Well done! Four! Well done. Two. That is too easy for you. Let's make it a little bit harder. I'm going to hold up my fingers, tell me the number that comes after. Excellent job. I held up five but what comes after five? Six. Too easy. Now tell me what comes before this number. Great job I had four what comes before four? Three. You're amazing. For this lesson, our learning intention is to solve subtraction problems using a number line and the counting back strategy. When we are subtracting it means you are getting less. Other words that mean the same as subtraction are minus decrease or take away. If you hear those words, it means we are using subtraction.

There are many ways to solve subtraction problems, but today I'm going to teach you one of my favorite ways and that is using a number line and the counting back strategy. If you have never heard of a number line before or the counting back strategy, please don't worry because you will know exactly how to use it by the end of today's lesson. I'm going to start with the equation on the board. Nine take away seven. I could use nine blocks or I could use nine pictures to help me solve my subtraction equation, but today I'm going to use my number line. When we have a subtraction problem, we always look at how many we have at the start. Here I started with nine so I'm going to circle the nine on my number line.

The problem says nine take away seven so we need to take off seven. When we are subtracting, you are always getting less, which means instead of moving up our number line, we will be moving down closer to zero. Here I need to take seven off the number nine. Watch me as I jump back seven places on my number line. One, two, three, four, five, six, seven. I have landed on the number two which shows me that nine take away seven equals two. I love using number lines and the counting back strategy because as you can see it is so much speedier than blocks or drawing pictures.

Let's have a look at another subtraction problem. I have five take away four. You can watch me as I solve this. I'm going to start with how many I had to begin with, which was five. I need to circle five on my number line. Now I need to write the equation again. It says five take away four. I need to take off four so instead of moving up my number line, I will be moving down closer to zero. I'm going to jump back four places. You can count with me if you like. One, two, three, four. As you can see we landed on the number one which means that five take away four equals one. Well done.

Now we are up to my favorite part of the lesson where we get to work as a team to solve a subtraction problem. The problem we need to solve is 10 take away three but before we do that, we need to learn how to set up a number line to help us solve a problem. So get ready with your pencil and paper and follow my instructions to create your very own number line. Our number line always starts with zero. You can put a zero on the left hand side of your page. Then our number line today is going to finish at ten. You can put a ten on the other side. Now we are going to spend this moment filling in the gaps. It's always very helpful to count out loud so that you don't miss a number on your number line. You can follow on from me so that your number line looks the same. Zero one, two, three, four, five, six, seven, eight and nine. As you can see, my number line is not perfect and yours does not need to be either. The next step is to add a line underneath. Going from zero all the way to the ten try to make it as straight as you can. Then we need to complete our number line by joining our numbers to the line like this. You can take this time now to do the same on your page.

Five, six, seven, eight, nine and ten. Our number lines are complete, which means we are now ready to tackle our subtraction problem which is ten take away three. Now remember our first job is to start with the total. We started with ten of something so we need to circle ten on our own number line. You can do that while I do mine.

Now that we have both circled ten we need to read our problem again to find out how many places we need to jump back on our number line. Ten take away three. How many places do we need to jump back? Three that's right. Do we jump higher than ten or closer back to zero? That's right. We are going closer to zero. We are moving down our number line because when you subtract you get less. I would like you to take the next five seconds to jump back three spaces. You have five, four, three, two, and one. Well done. I'm going to do this on my number line now. One, two, three. Did you land on number seven? Well done. That means that ten take away three equals seven. Great job. Let's try one more together. We already have our number line set up so we can get straight into the problem four take away four. we need to start with our first number, which is how many things we began with. That is four. Find four on your number line and circle it. I'll do the same. Now our job is to read the equation and decide how many places we need to jump back on our number line. Four minus four. How many places do we need to jump back? That's right. We need to jump back four and we always move closer to zero because when you subtract, you always get less. Start at your four and jump back four. You have five, four, three, two, one. What number did you land on? Let's see if mine will match yours. I'm going to jump back four places. One, two, three. and four. We have landed on zero, which means if you have four of something and take four of that something away, you end up with zero. Well done if you got zero as well, give yourself a little pat on the back. Great job. Thank you for being so sensational during that lesson. If you would like to continue to practice subtraction with a number line, I have a game you could play at home using a deck of cards, draw two cards, find the smaller number and take it away from the bigger number. Use your number line to find out what the answer would be to that problem. Thank you so much for joining me today and I can't wait to see you again soon.