Video: Adding by Making 10

Ethan is adding by making 10. Which calculation should he do first? [A] 9 + 1 = 14 [B] 9 + 5 = 14, Which calculation should he do next? [A] 10 + 6 = 16 [B] 10 + 5 = 15

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Video Transcript

Ethan is adding by making 10. Nine plus six equals what. Which calculation should he do first? Nine plus one equals 10 or nine plus five equals 14. And then which calculation should he do next? 10 plus six equals 16 or 10 plus five equals 15.

In this question, we can see that Ethan is adding two one-digit numbers together, nine plus six. And in the first sentence, we’re told how Ethan does this. He’s adding by making 10. Now, if Ethan wants to add nine and six together, why might he want to make 10? Or perhaps he knows that adding any number to 10 is a quick and an easy way to find an answer. And if we look at the diagram, we can see what Ethan’s done. We can see that he started off by writing the addition nine plus six. But he’s done something interesting to the number six. He split up the number six using a part-whole model. And he split it into the number one and five because one and five are two parts that go together to make six.

Now, why might Ethan have split the number six into one and five? Well, he wants to make 10. That’s why. And Ethan knows that if he puts one with nine, he can make the number 10. That’s how we know the calculation that Ethan should do first is nine plus one equals 10. Now, adding a number on to 10 is a quick and easy thing to do. So all Ethan needs to do to find the total is to add what’s left of the number six, the other part, which is five. This is how we know that the calculation Ethan needs to do next is 10 plus five equals 15. Ethan found the answer to nine plus six by splitting up the number six and using it to make 10. His first calculation was nine plus one equals 10. And then he added what was left of the number six. 10 plus five equals 15.

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