# Question Video: Exploring and Writing Different Addition Expressions to Make 9 Mathematics • 1st Grade

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### Video Transcript

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.