ShmoopTube

00:03

[Dino and Coop singing]

00:13

Do you ever feel like there’s something all around you? [Matrix style grid appears in front of a man]

00:16

Surrounding the place where you are?

00:18

Defining the limits of your world?

00:20

Uh, no…not the Force.

00:22

We’re talking about perimeter. [Man looks surprised]

00:24

Perimeter is the distance around the outside of a figure. [Coop pointing at a blackboard]

00:26

We could talk about the perimeter of a room…

00:29

… a building…

00:30

… a city…

00:31

… or anything, really.

00:32

And knowing the perimeter of a space can be pretty useful. [Boys hat blows off in the wind]

00:34

Say you need to know how much wood you should buy to build a fence that’ll keep your dog [Another hat lands on the boys head]

00:38

from running away…

00:39

… or maybe you want to know how much Justin Bieber wall-paper you’ll need for your bedroom. [Man looks shocked as his dog runs away]

00:43

In both cases, you need to know the perimeter. [Girl dances as Justin Beiber wallpaper appears]

00:45

So…how do we find perimeter?

00:48

Well, we actually have a choice, because there’s two –

00:51

-- yes, two different formulas to calculate the [A footpath that goes two different ways]

00:53

perimeter of a rectangle.

00:55

The first formula is simple and sweet.

00:57

You simply add the length of all four sides together, like this. [Dino pointing at a blackboard]

01:00

Then there’s the fancy formula.

01:02

It’s a little more challenging, but that just means you’ll feel even cooler when [Fancy formula folder]

01:06

you do it.

01:07

It’s done by doubling the length and the width and then adding them together. [Girl wearing shades]

01:11

So back to our examples…how big does that fence need to be to suppress your dog’s

01:16

wanderlust? [Fence appearing around the man's house]

01:17

First, figure out the length of all the sides of your yard.

01:19

Let’s say two sides are 2,500 feet long and two sides are 2,000 feet long. [Red line shows the sides of the yard]

01:25

Using the first formula, we can discover the perimeter by adding all four sides together.

01:29

And we discover the perimeter of our yard.

01:32

It's 9,000 feet.

01:33

And that Justin Bieber wall paper?

01:35

Let’s use our second formula for this one. [Girl holding the fancy formula folder]

01:37

That gives us double 15 feet plus double 12 feet…

01:41

And badda bing badda boom, the perimeter of the bedroom is fifty-four feet.

01:44

And that’s how you find perimeter of the space around you. [Man hammering in a beware of the dog sign]

01:47

Of course, neither formula can predict how high your dog can jump…

01:51

Man…he's like a little Houdini…. [Dog jumps over the fence and the man looks annoyed]

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