Video: Using the Break-Apart Strategy to Subtract within 20

Daniel started with 16. He took away 6 to make 10, then took away 2 more. Pick a calculation that is the same as what Daniel did. [A] 16 − 6. [B] 16 − 8. [C] 16 − 4.

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Video Transcript

Daniel started with 16. He took away six to make 10, then took away two more. Pick a calculation that is the same as what Daniel did. 16 take away six, 16 take away eight, or 16 take away four.

In this problem, we can see that Daniel is subtracting from a teen number. We know this for a number of reasons. We’re told that he starts with the number 16. We can see in the picture that there are 16 counters before some get crossed off. And all of our possible answers start with the number 16 too. So, we know that Daniel is trying to find the answer to 16 take away something. But what number is he trying to take away?

Well, if we read the question carefully and look at the pictures, we can see that Daniel finds the answer in two steps. First, we’re told he took away six. Now, why might Daniel split up his subtraction into two steps and only take away six to start with? Well, we’re told this again in the question. He took away six to make 10. We know this is a quick calculation to work out. 16 take away six leaves us with 10.

And you know by making 10 like this, what Daniel’s done is he’s made the calculation a lot easier cause now all he has to do is take away whatever’s left from 10. And we can subtract from 10 really quickly. We’re told that Daniel took away two more. And if we look in the bottom picture, we can see the two extra counters that Daniel’s taken away. It’s a quick way of finding the answer because Daniel probably knows that two and eight go together to make 10. So, if he subtracts two from 10, he’s going to be left with eight.

By reading the problem carefully and looking at the pictures, we can see exactly what Daniel is doing. First, he took away six, and then he took away two more. Daniel found the answer to 16 take away six take away two. And the calculation that’s the same as this is 16 take away eight.

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