Video: Embedding Understanding of Equivalent Expressions

﻿Hello everybody, my name is Miss Scully, and I will be taking your lesson today. This is your practise activity that you were sent in the previous lesson. So in the red box there are some expressions, and in the blue box there are also some expressions, and you needed to match the red expressions with the blue expression. So, 2 add 1, would match 1 add 2. Both expressions have a 2 and a 1. In the first expression in the red box, the 2 comes first, and the 1 comes second. In the second expression in the blue box, the 1 comes first, and the 2 comes second. The sum of both expressions is 3, so we can use the equal sign between them. 3 add 4 would match to 4 add 3. Both expressions, both have a 3 and a 4. In the first expression in the red box, the 3 comes first, and the 4 comes second. Whereas, in the second expression in the blue box, the 4 comes first and the 3 comes second. The sum of both expressions is 7, so we can use an equal sign between both of them. 1 add 6 would match to 6 add 1. Both expressions have a 1 and a 6 in them. In the first expression, in the red box, the 1 comes first, and the 6 comes second. Whereas, in the second expression, in the blue box, the 6 comes first and the 1 comes second. However, the sum of both expressions is 7, so we can use an equal sign between them. 5 add 2 would match to 2 add 5. Both expressions have a 5 and a 2 in them. In the first expression, in the red box, the 5 comes first and the 2 comes second. Whereas, in the blue box, in the second expression, the 2 comes first and the 5 comes second. The sum of both expressions is 7, so we can use an equal sign between them. 7 add 3 would match to 3 add 7. Both expressions have a 3 and a 7 in them. In the first expression, in the red box, the 7 comes first, and the 3 comes second. Whereas, in the second expression in the blue box, the 3 comes first, and the 7 comes second. The sum of both expressions is 10, so we can use an equal sign between both expressions.

In fact, I hope you spotted that you didn't need to do any adding up at all in this exercise, because all you needed to look for were the expressions that had the same addends in them, so 2 and 1 and 1 and 2, they both have a 1 and 2. 3 and 4, 4 and 3, they both have a 4 and 3. Because, we know that we can change the order of the addends and the sum remains the same.

Here is an equation. 1 add 6 is equal to 6 add 1. What do you notice about this equation? Pause the video to have some thinking time or to discuss with an adult nearby. I've noticed that 1 and 6 are on both sides of the equal sign. On the first side, the 1 comes first, and the 6 comes second. Whereas, on the second side, the 6 comes first, and the 1 comes seconds. Let's look at this as a story. Let's look at the first side again. First, one person is on the bus. Then six more people get on the bus. Let's look at the second side now. First, six people are on the bus, and one more person gets on the bus. Both sides sum to 7. Because both sides sum to 7, we can put an equal sign between both sides as they have equal value. Remember, we can change the order of the addends, and the sum remains the same. Here is another equation. 2 add 3 is equal to a missing addend add 2. What do you notice about this equation now? Pause the video if you want some thinking time or to discuss with an adult, if you can. Let's look at the first side of the equal sign. I've noticed that there is a 2 and a 3. Let's look at the second side. On the second side, there is a missing addend, which comes first, and 2, which comes second. Let's look at this as a story. Let's look at the first side. First, two people are on the bus. Then, three more people get on the bus. Let's look at the second side now. First, we don't really know how many people are on the bus, but we do know that 2 more people join them. I know that both sides are equal in value, because of the equal sign here. Both sides sum to 5. Because, both sides sum to 5, and that there is an equal sign between them, it means that the missing addend must be 3. Remember, we can change the order of the addends, but the sum remains the same. Here is another equation. 3 add 5 is equal to 5 add missing addend. What do you notice about this equation? Pause the video to have a think or discuss with an adult if you can. Let me tell you what I can see. On the first side of the equal sign, I have noticed that 3 comes first and 5 comes second. But on the second side, I have noticed that 5 comes first and the missing addend comes second. Let's look at this as a story. I'd like you to get your hands ready, and you've got your first hand and your second hand. So, look at the first side. Hand one has three fingers, and hand two has five fingers. Look at the second side. Hand one has five fingers, but I don't know what the other hand has, my second hand, hand two. But I do know that both sides are equal in value, because I've got my equal sign here. The sum of 3 and 5 is 8. And, because both sides are equal in value, that means that this side also had to have a value of 8, meaning that my missing addend must be 3. And, remember we can change the order of the addends, and the sum remains the same. Here is an equation. 6 add a missing addend is equal to 3 add 6. What do you notice about this equation? Pause the video to think and discuss with someone if you can. Do you know the missing addend already? Think about our generalisation below. We can change the order of the addends and the sum remains the same. Look at the first side of the equal sign. On the first side, I've noticed that there is a 6 and a missing addend. But on the second side, the 3 comes first, and the 6 comes second. I know that both sides are equal in value. Both sides must sum to 9. Because both sides sum to 9 and that there is an equal sign between them, it means the missing addend must be 3. Let's play a game of true or false. True or false? 2 add 1 is equal to 1 add 2. Pause the video if you want to think or to discuss with an adult. Now, the answer is true. And the reason why is this. On the first side of the equal sign, there is a 2 first and a 1 second. On the second side of the equal sign, 1 comes first and 2 comes second. I know this is true, because the addends are the same on both sides of the equal sign. On the first side, 2 comes first, and on the second side the 2 comes second. On the first side, the 1 comes second, and on the second side, the 1 comes first.

In fact, with this one, I bet you knew it was true straight away, because both sides of the equation have the same addends, don't they? Yes, they're swapped over, the order's different, but that doesn't matter, because we know we can change the order of the addends and the sum remains the same.

Here is your practise activity for today. I have written two patterns of numbers. Can you spot my pattern, and can you fill in the missing addends? Afterwards, if you would like a challenge, can you come up with your own pattern of numbers using some really, really big numbers? Don't forget, we can change the order of the addends and the sum remains the same.

Lesson summary: Embedding Understanding of Equivalent Expressions

This lesson embeds understanding of equivalent expressions.

Maths

Y1 Maths

Key Stage 1

Year 1