Question Video: Finding All Ways to Subtract from 7 | Nagwa Question Video: Finding All Ways to Subtract from 7 | Nagwa

Question Video: Finding All Ways to Subtract from 7 Mathematics

Liam is subtracting from 7. Write the missing number sentence.


Video Transcript

Liam is subtracting from seven. Write the missing number sentence. Seven take away one is six. Seven take away two is five. Seven take away three is four. Seven take away four is three. What? Seven take away six is one.

In this question, Liam is taking away or subtracting from the number seven. We know this because we’re told this in the first sentence. We can also see that on each of his ten frames, he’s put seven black counters to start off with. And we can also see that the first number in every number sentence is seven. It’s the number Liam is starting off with each time. And so the first thing we can say about our missing number sentence is it’s going to begin with the number seven. What’s the next thing we can say?

Well, because this is a subtraction number sentence, we need to take away a number. But how many should we take away? If we look carefully at Liam’s pictures, we can see that he’s taking away in a certain order. In the first ten frame, he’s crossed out or taken away one counter, then two counters in the second ten frame. Then he takes away three, then four. He’s taking away one more each time, isn’t he? And one more than four is five. Our missing number sentence shows seven take away five.

Now, we could find the answer by counting the number of black counters that haven’t been taken away. But we could also find the answer by looking at our number sentences, in particular, the answers. Our first answer is six, then five, four, three. Can you see a pattern here? Liam is taking away one more counter each time. And so his answer is getting one less each time. His last answer was three. So his next answer, the one we’re looking for, is going to be one less than three. We would expect it to be two.

Now, does that number sentence make sense? Is five and two a pair that make seven? Yes, they are. Liam’s missing number sentence is seven take away five is two.

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