Video Transcript
Sides of 2D Shapes
In this video, we’re going to learn
how to identify and count the sides of 2D shapes.
This is Larry. He’s been hired to paint the white
lines on a sports field. But there’s one thing about
Larry. Once he gets going, he can only
paint straight lines. This leads to him painting some
very interesting 2D shapes. What happens if he paints a
square? He paints one, two, three, four
straight lines. And you know we can call these
straight lines the sides of the shape. A square is made up of one, two,
three, four straight sides. And one thing we know about the
sides of a square is that they’re all the same length.
I think Larry might be about to
paint another shape. How many sides are there on this
shape? We could find out how many this
time by placing a counter on each side. This shape is made up of one, two,
three straight sides. Can you remember the name of the
shape that Larry’s painted? It’s a triangle. Triangles are shapes that have
three straight sides.
Oh, it looks like Larry’s really
got carried away this time. He’s painted a shape just like the
first letter of his name. How many straight lines did Larry
need to paint to paint this shape? To make sure we count each line
only once, let’s trace over them in different colors. One, two, three, four, five,
six. Six straight lines means six
sides. We could say that Larry has painted
a six-sided shape.
So, how well do you think you can
find and count the sides of 2D shapes? Shall we have a practice? Let’s try some questions where we
have to use this skill.
Which of the given shapes has four
sides?
We’re shown a picture here of four
different 2D or flat shapes. We can see that each of the shapes
is made up of a number of straight lines. We call these straight lines the
sides of the shape. Now, each of these shapes has a
different number of sides. But we’re asked to find the shape
that has four sides. Let’s count the sides on each shape
to find out which one it is.
We could put a counter on each side
to show that we’ve counted it. The first shape has one, two,
three, four, five sides. This isn’t the shape we’re looking
for. We’re looking for a four-sided
shape. Let’s try the next one. Do you recognize this next
shape? It’s a triangle. And the one thing that we can say
about triangles is that we can draw them by joining up three straight lines. They have three sides. So, this isn’t our shape
either.
Our third shape has one, two,
three, four sides. It looks like this is the shape we
were looking for. And if we just check the final
shape, we can see that this has six sides. So, we’ve identified the shape that
has four sides. And you know what the name of that
shape is? It’s a square. Each of the four sides is the same
length. And if you think that this doesn’t
look like the usual way you draw a square, turn your head slightly. This is just a square that’s been
turned a bit. That’s all. This is the shape that has four
sides.
True or false? Shape A and shape B have the same
number of sides.
Underneath the question, we can see
pictures of two shapes. And both of these shapes have been
made from straight lines. We call these straight lines the
sides of the shape. Our question is made up of a
statement which tells us that shape A and shape B have the same number of sides. In other words, these 2D shapes are
made up of the same number of straight lines.
But this statement might not be
correct. We need to decide whether it’s true
or false. To make sure that we count all the
sides of a shape and also that we only count each one once, let’s trace over them as
we count them. Let’s start from here on shape A,
which is made up of one, two, three, four sides. We can say shape A is a four-sided
shape.
Now, let’s trace over the sides of
shape B. We’ll start from this bottom
corner. There are one, two, three, four
sides again. Although shape 𝐵 is a different
sort of shape to shape A, it’s still a shape with four sides. We’ve counted the number of sides
that make up each shape. And we can see that they’re both
the same. The statement in the question is
true.
Jacob has built a square with four
sticks. How many sticks does he need to
build a triangle?
You know, we can draw 2D
shapes. But, in this question, Jacob has
built one. We’re told that Jacob has used four
sticks to build his shape. They look a bit like ice lolly
sticks, don’t they? And the question tells us that the
name of Jacob’s shape is a square. And in the picture, we can see the
four sticks that he’s used. One, two, three, four. Why has Jacob used four sticks to
build his square? Why hasn’t he used two or three or
five?
Well, we know the reason why Jacob
has used four sticks is because squares have four straight sides. And each side is the same
length. So, it’s very easy to do when all
your lollipop sticks are the same length. Squares have four sides.
Now, our question goes on to ask
us, how many sticks does Jacob need to build a triangle? And to answer the question, we’re
going to have to think how many straight sides does a triangle have. We know that to draw a triangle, we
need to draw one, two, three straight lines. Triangles are shapes that have
three sides. And so, Jacob can build his
triangle out of one, two, three sticks.
Although it didn’t mention the word
in it, this question was all about the sides of 2D shapes. We know that squares have four
sides. And that’s why Jacob could build
his square using four sticks. And we also know that triangles
have three sides. And that’s why the number of sticks
that Jacob’s going to need to build his triangle is three.
So, what have we learned in this
video? Firstly, we’ve learned that the
straight lines that form a shape are its sides. We’ve also learned how to identify
and count the sides of 2D shapes.
