Video: Solving Word Problems by Partitioning Rectangles into Rows and Columns

Emma baked a tray of brownies. She cut them into 5 rows and 3 columns so that all the brownies were the same size. Which model shows how Emma cut the brownies? How many brownie squares did she bake?

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Video Transcript

Emma baked a tray of brownies. She cut them into 5 rows and 3 columns so that all the brownies were the same size. Which model shows how Emma cut the brownies? How many brownie squares did she bake?

The question gives us some important information about what Emma does when she bakes a tray of brownies. She cuts them into five rows and three columns. We know that a row of shapes — in this case, squares — is when we have a line of them going across and a column of squares is when we have a line of them going up and down. We’re given four models, but only one of them shows us how Emma cut her brownies. Let’s go through them to work out which one it is.

Our first model contains two rows. So this is clearly not the five rows and three columns that we’re looking for. But we can see where the numbers five and three do come with this model. The first row contains five squares and the second row contains three squares. This is not the model we’re looking for. If we count the number of rows in our second model, we can see that there are five this time. But how many columns are there? One, two, three — this is going to be larger than the three columns we’re looking for — four, five. This model is not correct either.

Our next model also contains five rows. But how many columns are there? One, two, three. There are five rows and three columns. This is the model that shows us how Emma cut the brownies. We have to be careful with our answer because it might be easy to choose the last model instead. This model shows five columns and three rows, not five rows and three columns. So we have to be careful not to make this mistake.

The second part of our problem asks us how many brownie squares did she bake. Now, we know that Emma cut her tray into five rows. And because she then cuts the tray into three columns, each of the five rows then had three squares of brownie in it. They’re all the same, and they all contain three squares. We can see five groups of three. So to find the total number of brownie squares, let’s count in threes five times: three, six, nine, 12, 15. If we cut a shape into five rows and three columns, we have 15 parts altogether.

The model that shows how Emma cut the brownies is the one that shows five rows and three columns. The number of brownie squares that Emma baked is five groups of three. The answer is 15.

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