Lesson Video: Addition of Three Numbers within 20 by Making Ten Mathematics • 1st Grade

In this video, we will learn how to add three numbers whose sum is at most 20 by finding two of them that sum to ten.

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Video Transcript

Addition of Three Numbers within 20 by Making 10.

In this video, we will learn how to add three numbers by first finding two numbers which make 10. When we’re adding three numbers together, we can use a ten frame to help us to look for pairs of numbers which make 10. So this frame has one blue counter and nine green counters. One and nine makes 10. Let’s go through all the pairs of numbers which make 10: one plus nine, two plus eight, three plus seven, four plus six, five plus five, six plus four, seven plus three, eight plus two, nine plus one, and we could also have 10 plus zero or zero plus 10. These are all the pairs of numbers which make 10.

Now let’s practice adding together three numbers by first finding a pair which makes 10.

In this question, Michael started putting counters into 10 frames to help him add.

Can you find the total? Six plus four plus seven. So we have to calculate six plus four plus seven. Michael has already moved six orange counters into a ten frame. He’s also put four blue counters into the same ten frame. This tells us that six plus four makes 10. We found a pair which makes 10. Now all we have to do are add the seven green counters to the other ten frame. So we can calculate the answer by adding 10 and seven. 10 plus seven is 17. So we’ve found the answer to six plus four plus seven by making a pair that totals 10; six plus four makes 10. And then we added the seven to find the answer 17.

Let’s practice one more example.

Answer the questions to find an easy way to add six and three and seven. What is seven plus three?

We can use our ten frame to show that seven plus three makes 10. The next question asks what is six plus 10. Six plus 10 is 16. And the final part of the question asks us what is six plus seven plus three? We already know that seven plus three makes 10 and six and 10 makes 16, so six plus seven plus three equals 16.

In this video, we’ve learnt how to add three numbers by first looking for pairs of numbers that make 10.

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