# Video: KS1-M16S • Paper 2 • Question 21

Draw a line of symmetry on each of these shapes.

03:08

### Video Transcript

Draw a line of symmetry on each of these shapes.

We can see three shapes: a rectangle, a triangle, and a star. We’re asked to draw a line of symmetry on each of the three shapes. But what is a line of symmetry? Let’s remind ourselves. A line of symmetry is a line that we can draw on a shape that splits it into half so that both sides of the shape on either side of the line are exactly the same. It acts a little bit like a mirror line the shape on one side of the mirror line is exactly the same as the shape on the other side of the mirror line. And so, it’s a little bit like one side of the shape reflect across the line of symmetry onto the other side of the shape. Both halves are exactly the same.

So let’s start by thinking about the rectangle. Where we should draw the line of symmetry on this rectangle? What if we draw it here? Well, we can see that although this line has divided the shape into two parts, they’re not the same. We need to draw our line of symmetry so it acts like a mirror line. So we need to draw our line of symmetry here. Both sides of the line of symmetry are exactly the same. And if we imagine this rectangle was a piece of paper, we could fold the piece of paper along this line of symmetry and both sides would fold exactly on top of each other.

Let’s think about the triangle. Where could we draw our line of symmetry on this triangle? Well, we can draw it vertically, just like we did with the rectangle. We’ve divided the triangle into two more triangles. And if we look, both of the two triangles are exactly the same. They are reflections of each other. And again, if we imagine our triangle cut out of paper and we folded it, it would fit on top of each other. I wonder if there is a vertical line of symmetry with a star too. Yes, there is. Both halves of the star are exactly the same. They’re reflections of each other.

We drew a line of symmetry on each of the shapes by thinking where we could draw a line that splits the shape into two equal parts so that one part was a reflection of the other part. This is an interesting question because there are actually other ways to draw lines of symmetry for the rectangle and the star. And these will be correct if you drew them. If you have a moment, why not you turn your head and look at the shapes from different positions and try to spot where the other lines of symmetry might be?