Video: Using the Division Symbol to Write Equations to Find the Number of Items in Equal Groups

Natalie is preparing breakfast. She made 20 sandwiches and put them on 10 plates. Choose the calculation that is equal to the number of sandwiches on each plate. [A] 20 − 10 [B] 20 ÷ 2 [C] 20 + 10 [D] 20 ÷ 10. How many sandwiches are on each plate?

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Video Transcript

Natalie is preparing breakfast. She made 20 sandwiches and put them on 10 plates. Choose the calculation that is equal to the number of sandwiches on each plate. 20 take away 10, 20 divided by two, 20 plus 10, or 20 divided by 10. How many sandwiches are on each plate?

This problem describes Natalie who’s preparing a really big breakfast. Perhaps she’s made it for her whole class because she’s made 20 sandwiches. But you know, she hasn’t just put them in one big group; she split them up. We know this because we’re told that she’s put the 20 sandwiches on 10 plates. We could say she’s shared them out. And we can see a picture to help us.

In the first part of the problem, we’re told to choose the calculation that is equal to the number of sandwiches on each plate. And we’re given four possible calculations to choose from. Now, we can see in the picture how many sandwiches are on each plate. But if we didn’t have the picture to help us, which of these calculations would we use?

To find the answer, we need to think carefully about what Natalie’s done here. The first thing that she’s done is to make 20 sandwiches. So, this is the number she begins with, 20. But then, what does she do? She puts them on 10 plates, doesn’t she? And if we look at each plate, we can see that they all have an equal number of sandwiches on. These 20 sandwiches have been shared out. And another word for “shared” is “divided.” And the symbol that we use when a number is divided into equal groups is the division symbol, which is a line with two dots either side.

How many equal groups has Natalie made? Well, she shared out her sandwiches onto 10 plates. So, she’s divided 20 by 10. To find out the number of sandwiches on each plate then, we need to find the answer to 20 divided by 10. And if we look at our four calculations, this is one of them.

We might use 20 take away 10 if we wanted to find out how many sandwiches Natalie had left after making 20 and then eating 10 of them. 20 divided by two is a division calculation. But this would be the number of sandwiches in each group if Natalie shared them onto two plates. And we know that adding is to find the total of two numbers. So, 20 plus 10 would be to find the number of sandwiches if Natalie perhaps made 20 sandwiches and then made another 10.

So, that’s how we know the correct answer is 20 divided by 10. And we can use this to calculate the number of sandwiches on each plate. 20 divided by 10 equals two. 10 groups of two make 20. So, if Natalie makes 20 sandwiches and puts them on 10 plates, the calculation that’s equal to the number of sandwiches on each plate is 20 divided by 10. And the number of sandwiches that are on each plate is two.

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