Question Video: Completing Symmetrical Patterns Using Mirror Lines

Emma is making a symmetrical pattern. She has drawn her mirror line. What is the missing part of her pattern?

02:59

Video Transcript

Emma is making a symmetrical pattern. She has drawn her mirror line. What is the missing part of her pattern?

We’re told that Emma has made a symmetrical pattern and we can see a picture of it. Let’s remind ourselves what the words symmetrical pattern mean. When something symmetrical, it’s the same on both sides. That’s why the idea of a mirror is really useful when we’re thinking about symmetry. A mirror reflects what’s in front of it, and it looks the same on both sides. We’re told in the question that Emma has drawn her mirror line. Can you see where it is? Here it is, let’s label it in a bright color so it stands out for us.

Now, this mirror line is important. It’s in the very center of Emma’s pattern. And because Emma’s pattern is symmetrical on either side of the mirror line, the shapes are the same. Up close, next to the mirror line at the top, we have two yellow squares, and the next two shapes along are the same. We have two blue triangles. Now, although Emma is making a symmetrical pattern, she hasn’t quite finished it yet. There’s a part to her pattern that’s missing, and we’re asked, what is the missing part of her pattern? We need to think of the shapes that belong in this space.

Now, you may think it’s got something to do with these two shapes that are at the bottom, the pink circle and the blue triangle. And you know what? You’d be right. Now, it would be very easy to look at these shapes and to think, “Well, it must be the same on both sides.” The answer’s got to be a pink circle and a blue triangle. Well, if you think the answer is this, you’re almost there, but the answer is not quite right. And we can see why if we put these shapes into position. Can you spot the mistake? If we start from the mirror line, just like before, and we compare the shapes on either side, we start with a blue triangle on one side, but the shape on the other side doesn’t match. It’s not the same, and neither do the next two shapes along.

Can you see what we need to do to make the pattern symmetrical? You’ve got the right shapes, but they’re not in the right order. The nearest shape to the mirror line needs to be a blue triangle and then the pink circle. Can you see how the shapes match now? The pattern is the same on both sides of the mirror line. It’s symmetrical. The missing part of Emma’s pattern is a blue triangle followed by a pink circle.

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