Question Video: Subtracting Numbers up to 10 by Subtracting from 10 Mathematics • 1st Grade

Fill in the blank: 10 − 7 = _. Fill in the blank: 15 − 7 = _.

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Video Transcript

Fill in the blank: 10 take away seven equals what. And then fill in the blank: 15 take away seven equals what.

This question has two parts. And did you notice? They’re linked. In both parts, we need to take away seven. In the first part, we’re asked to start with 10 and take away seven. But then, in the second part, we need to find the answer to 15 take away seven. And why do you think we’re given two similar calculations like this one after another? Do you think maybe the first calculation might help us find the answer to the second? Let’s find out. Now there’s a reason why we don’t have a 10 frame to help us with this first question because taking away numbers from 10 is quite quick and easy to do. We just need to remember the facts we know about the numbers that go together to make 10.

Now do you remember what goes together with seven to make 10? We know that seven and three makes 10. And so if we start with 10 and take away seven, we’re going to be left with three. So if 10 take away seven equals three, how could we use this to help us find the answer to 15 take away seven. Well, this is where our 10 frames come in useful because they help us to see that the number 15 is made up of 10 and five ones. And so if we want to take away seven from 15 really quickly, we can just start by looking at this one 10 because we know how to take away seven from 10 really quickly. As we’ve said already, 10 take away seven is going to leave us with three.

So to find the answer to 15 take away seven, we just need to add the three ones that we’ve got left with the five ones over here. And we know that three plus another five equals eight altogether. And that’s how we know that 15 take away seven equals eight. We’ve used a fact to do with subtracting from 10 to help us take away from a teen number. 10 take away seven equals three. And so we know that 15 take away seven equals eight.

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