Adding One-Digit Numbers by Making 10
In this lesson, we’re going to learn how to add two one-digit numbers together by first making 10. Now, before we start, let’s remind ourselves about something. And this is the fact that adding a number on to 10 is quick and is also easy. We know that 10 plus two equals 12. Five more than 10 is 15. As we’ve just said, adding a number on to 10 is quick and easy. Perhaps you can see the patterns in the numbers that we’re adding and the totals that we get. Now, in this video, we’re going to be adding two one-digit numbers together. But because adding a number on to 10 is quick and easy, we’re going to make one of the numbers into 10 first. Let’s see how we do this.
Now, let’s imagine that we’ve got a packet of cookies and we open it. And we tip out two piles of cookies. We have a pile of seven cookies and six more cookies. And to find the total, we need to add seven and six together. Now, one way we could model this addition is using ten frames. Seven plus six equals what? Now, we could find the answer by starting with the number seven and counting on six more. But in maths, it’s always good to find quick and easy ways to find the answer.
Now, we know that adding numbers to 10 is quick and easy. What if we split up the number six and move some of our cookies into the first ten frame so that we make 10? Then we’d be adding 10 and another number together. That would be quick and easy to do. What number do we know goes with seven to make 10? Well, we know that seven and three make 10. And so we’re going to have to split up our six cookies into the three cookies that we’re going to move and then three more cookies that are left behind because we know three and three makes six.
Let’s move our three cookies across. We filled up the first ten frame. Instead of there being seven cookies, we now have three cookies more, which gives us a total of 10. Now that there are 10 cookies in our first ten frame, all we have to do is to add what’s left of the number six. We only have three cookies left. So by making 10, look at how we’ve turned our addition into something we can work out quickly and easily, 10 plus three. 10 plus three equals 13. And so we know that seven plus six must be worth 13 too. We’re going to try answering three different questions now. And each time we’re going to be adding together two one-digit numbers. But each time we’re going to be thinking about how to make the question quicker and easier to answer by making 10.
Find an expression that has the same answer as six plus eight.
Underneath the numbers six and eight, we can see two ten frames, and these are going to help us to answer the question. There are six pink squares and eight blue squares. We can see that the eight blue squares have been split up. Four of them have been moved across to the first ten frame. To do this, we’ve had to split up the number eight into four. These are the four that we’ve moved. And we have four left. We know that four and four go together to make eight. By putting some of our eight squares into this ten frame, we’ve managed to fill it. Six and four go together to make 10.
All that we have to do to find the same answer is to add on what’s left of the number eight, which is four. So we can say that an expression that has the same answer as six plus eight is 10 plus four. And you know, by splitting up the number eight to make 10 like this, we can make the calculation much easier to work out. The expression that has the same answer as six plus eight is 10 plus four.
Ethan is adding by making 10. Nine plus six equals what. Which calculation should he do first? Nine plus one equals 10 or nine plus five equals 14. And then which calculation should he do next? 10 plus six equals 16 or 10 plus five equals 15.
In this question, we can see that Ethan is adding two one-digit numbers together, nine plus six. And in the first sentence, we’re told how Ethan does this. He’s adding by making 10. Now, if Ethan wants to add nine and six together, why might he want to make 10? Or perhaps he knows that adding any number to 10 is a quick and an easy way to find an answer. And if we look at the diagram, we can see what Ethan’s done. We can see that he started off by writing the addition nine plus six. But he’s done something interesting to the number six. He split up the number six using a part-whole model. And he split it into the number one and five because one and five are two parts that go together to make six.
Now, why might Ethan have split the number six into one and five? Well, he wants to make 10. That’s why. And Ethan knows that if he puts one with nine, he can make the number 10. That’s how we know the calculation that Ethan should do first is nine plus one equals 10. Now, adding a number on to 10 is a quick and easy thing to do. So all Ethan needs to do to find the total is to add what’s left of the number six, the other part, which is five. This is how we know that the calculation Ethan needs to do next is 10 plus five equals 15. Ethan found the answer to nine plus six by splitting up the number six and using it to make 10. His first calculation was nine plus one equals 10. And then he added what was left of the number six. 10 plus five equals 15.
Scarlett added nine and seven by making 10. What number is missing from her solution? Nine plus seven equals 16. 10 plus what equals 16.
To understand what Scarlett’s done here, we could try to answer the question ourselves. And we’re going to try to make the addition, nine plus seven, a little easier to work out by making 10. Here’s what nine plus seven might look like using two ten frames. And one way to find the answer, we could start with the number nine and then count on seven more. But you know, adding a number to the number 10 is always a quick way to find the total. So what we can do to help ourselves is to turn the number nine into 10.
What goes with nine to make 10? Well, we know nine plus one more makes 10. To find the extra one that we need, we’re going to split our number seven up into one and whatever is left. And we know that one and six make seven. We can show this using our ten frames by moving across one counter. Now, we’ve made 10 in the first ten frame. We just need to add the six counters in the second ten frame. We’ve turned our calculation nine plus seven into 10 plus six. 10 plus six is 16. And so we know that nine plus seven must be 16 too. Scarlett added nine and seven by making 10. The number that’s missing from her solution is the number six. 10 plus six equals 16.
Now, what have we learned in this video? Well, firstly, we’ve reminded ourselves that we can quickly add numbers on to 10. And so we’ve learned how to add two one-digit numbers together by first making 10.