Video: Making 8 and 9

In this video, we will learn how to use pictures and addition equations to show all the different ways to make the numbers 8 and 9.

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Video Transcript

Making Eight and Nine

In this video, we will learn how to use models and addition equations to show all the different ways to make eight and nine. We could use cubes to help us find all the ways to make eight. We can see from the model that we can make eight using one red cube plus seven blue cubes. One and seven is eight. We could also make eight using two red cubes and six blue cubes. One plus seven is eight. Two plus six is eight.

Can you predict what the next number bond would be? In the first number bond, we had one red cube. In the second, we had two. We’re increasing the number of red cubes by one each time, one, two, three. We can make eight using three red cubes, but how many blue cubes? The number of blue cubes is decreasing by one each time. We’re taking away one blue cube each time, seven, six, five. So far, we found three different ways to make eight: one plus seven, two plus six, and three plus five.

It helps to use a strategy to find all the possible ways of making a number. We started with one red brick. We added one red brick each time and took away one blue brick each time. This helped us to find all the possible ways of making eight. We didn’t find all the possible ways of making eight. We’re going to do that with some practice questions.

We call the pairs of numbers which make nine number bonds to nine. Seven and two makes nine. Seven blue bricks and two red bricks is nine. We didn’t record all the ways of making nine or use a strategy. Let’s practise, finding all the ways to make eight and nine using models and addition equations.

There are lots of ways to make eight. What is the missing expression? Zero plus eight. One plus seven. Two plus six. What plus what. Four plus four. Five plus three. Six plus two. Seven plus one. And eight plus zero.

There are nine ways to make eight, but one of the expressions is missing. We could use the cube train to help us find the missing expression. We could also find the missing expression by working out the strategy that’s been used. If we look carefully at the pairs of numbers or the number bonds, we can spot some patterns.

If we write down the number of red bricks and blue bricks we’ve used to make eight, that will help us to spot the pattern. What’s happening to the number of red bricks? Zero, one, two, three, four, five, six, seven, eight. The number of red bricks is going up by one each time. We’re counting in ones. Now we found the first missing number. Zero, one, two, three.

What’s happening to the number of blue bricks? Eight, seven, six. The missing number is five. Eight, seven, six, five, four, three, two, one, zero. The number of blue bricks is getting smaller each time; it’s decreasing. We’re counting back in ones, eight, seven, six, five. The missing expression is three plus five. Zero and eight make five, one and seven, two and six, and three and five. So do four plus four, five plus three, six plus two, seven plus one, and eight plus zero.

We found all the ways to make eight using our model and a strategy. We wrote the number bonds down and looked for the pattern. This helped us to find the missing addition expression. Three plus five makes eight.

Find the missing addition sentence. Nine plus zero is nine. Eight plus one is nine. Seven plus two is nine. Six plus three is nine. Five plus four is nine. What plus what is nine. Three plus six is nine. Two plus seven is nine. And one plus eight is nine.

The model shows all the number bonds to nine. The pictures use blue and green tennis balls to model the addition expressions. Let’s look more closely at the strategy that’s been used to find the pairs. In other words, let’s look closely at the numbers in the number bonds. Let’s see if we can spot any patterns.

Nine blue tennis balls and no green tennis balls makes nine. Eight and one is nine. Seven and two is nine. Six and three is nine. Five plus four is nine. Have you spotted the pattern yet? Did you notice what’s happening to the number of blue balls each time? Nine, eight, seven, six, five. The numbers are decreasing. The number of blue balls is going down. There’s one less blue ball each time. Which number would come next? Nine, eight, seven, six, five, four.

Now we need to work out the number of green balls. Let’s see if we can spot the pattern. Zero, one, two, three, four, five. The number of green balls increases by one each time. We’re adding one green ball each time. The missing addition sentence is four plus five is nine.

We found the missing addition sentence by looking closely at what happened to the number of blue and green balls each time. We could use the model to help us check the answer. Are there four blue balls? One, two, three, four. Yes, there are. Let’s check there are five green balls. One, two, three, four, five. Four plus five is nine.

Think about making eight. Find the missing numbers. What plus one equals eight. Three plus what equals eight.

We’re given two addition expressions which make eight. Something plus one equals eight and something plus three equals eight. What do we add to one to make eight? To find the answer, we could count the number of squares. One, two, three, four, five, six, seven. Seven plus one equals eight.

Let’s find the missing number in the second pair of numbers. Three and what makes eight. Three and one, two, three, four, five makes eight. Seven add one equals eight. Three add five equals eight. The missing numbers are seven and five. We used part-whole models and bar models to help us find the missing numbers.

What number is missing? Nine is five and what more.

Let’s use a part-whole model to help. We know that the two groups of counters make nine. We know that five blue counters and a number of orange counters total nine. How many orange counters are there? One, two, three, four. Nine is five and four more. We used the number of counters and a part-part-whole model to help us find the missing number. Nine is five and four more.

What have we learned in this video? We’ve learned how to use models and addition equations to show all the ways to make eight and nine.

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