Video Transcript
Help Emilia find 17 plus 14. Amelia moves three ones. What sum has she made? What is 17 plus 14?
In this problem, we can see that Amelia is trying to find the sum of two numbers, 17 and 14. And we’re told to help her find the answer. The diagram shows us how Emilia’s found the answer. She’s used towers of cubes to help her. Let’s model what Emilia’s done, and it’s going to help us to answer the questions. The first thing that Amelia does is to model the first number in her addition out of cubes. 17 is made of one, 10, and seven ones. And she’s also modelled the second number in her addition. 14 is made up of one 10 and four ones.
We’re told in the first part of our question that Amelia moves three ones. And if we look at the diagram, we can see where she does this. Let’s draw what happens. She takes three of her four ones in 14. We’ll colour them green so we can see them more easily. And she moves them so that they’re added to the seven ones in 17. We can see that by doing this, Amelia has changed her calculation. By adding three ones to seven ones, she’s made another group of 10 ones. And she’s changed the calculation.
The question asks us, what sum has she made? Instead of 17, by adding three ones, Amelia now has two tens and no ones. She’s turned 17 into 20. And by moving her three ones from 14, she’s now left with one 10 and one one. That’s 11. Amelia now needs to find the sum of 20 and 11, which is a lot easier to do than to find the sum of 17 and 14. But the answer will be exactly the same.
The second part of our problem asks us, what is 17 plus 14 now? Are we going to add 17 and 14 together to find the answer? No, we need to use Amelia’s method. It’s made the calculation a lot easier. Let’s add 20 and 11 together. First, we’ll add the tens. We have one, two, three tens. Our answer is going to be 30 something. How many ones do we have to add? The number 20 has zero ones, but the number 11 has one one. And so, we have one one in total.
We’ve added 20 and 11 to find the answer, 31. And because all Amelia did was move three ones, we know that 20 and 11 has the same total as 17 and 14. Amelia moved three ones to make the calculation 17 plus 14 easier. By doing this, she made the addition 20 plus 11. We used this easier calculation to help us find the answer. 17 plus 14 equals 31.
