Question Video: Recognizing Area as an Attribute of Plane Figures Mathematics • 3rd Grade

Charlotte has drawn a shape with an area of 12 square units. Which two shapes have an area that is different from Charlotte’s shape?

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Video Transcript

Charlotte has drawn a shape with an area of 12 square units. Which two shapes have an area that is different from Charlotte’s shape?

Charlotte has drawn this shape. And we’re told her shape has an area of 12 square units. So Charlotte’s shape covers 12 squares on the grid. This is how much space her shape takes up. We’re shown another three shapes: shape one, shape two, and shape three. We have to choose the two shapes that have an area that is different from Charlotte’s shape. In other words, we have to find two shapes that do not have an area of 12 square units.

To find the area of each shape, we just need to count the number of square units it covers. Let’s start with shape one. Here’s two squares, and another three makes five squares. Five and two more is seven, and one more makes eight. Now we need to count the triangles. Each of these triangles is half a square. So if we put two halves together, we’ll make one whole square. So if we put these two halves together, we’ll have nine squares. These two halves make another whole square, which makes 10. Two more halves makes 11 squares. And we’ve got a half left over. So the area of shape one is 11 and a half square units.

We know that Charlotte’s shape has an area of 12 square units. So we know that shape one has an area which is different to Charlotte’s shape. Now we just need to find our second shape. What’s the area of shape two? Let’s count the number of squares. One plus three makes four, five, six, seven. Two more than seven is nine. Another two makes 11. 12, 13, 14. So the area of shape two is 14 square units. This is the second shape that has an area different from Charlotte’s shape, because the area of Charlotte’s shape is 12 square units. The two shapes that have an area different from Charlotte’s shape are shape one and shape two.

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