ShmoopTube

00:02

[Dino and Coop singing]

00:12

People who build fences need all sorts of tools and materials: shovels, wood, concrete, [Man holding a toolbox]

00:17

Slurpees…

00:17

What?

00:18

Building a fence is hard work.

00:19

But they also need a more mathematical tool: the concept of perimeter. [Math problems floating around]

00:23

What's the concept of perimeter?

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We're glad you asked!

00:27

…No seriously.

00:28

Otherwise, we would've made this entire video for nothing. [Kid with his hands on his hips looks unconvinced]

00:30

Perimeter is the distance around the outside of an object or a space.

00:34

So let's take a look at this pool.

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And for now let's only look.

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We only get to do cannonballs after the math is done. [Man goes to jump in the pool and stops midair]

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If we want to measure the pool's perimeter, we need to measure the lengths of each of [An arm pulls the man away from the pool]

00:44

its four sides…

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…and then add them all together.

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So let's do it.

00:48

If we measure the width, we see that it's fifteen feet.

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And if we measure the length, we see that it's twenty feet.

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So to find the perimeter, we need to add one length…

00:57

…to one width…

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…to the other length…

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…and to the other width…

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…which gives us the grand total of seventy feet.

01:02

Time for a celebratory cannonball! [Man jumps into the pool]

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We should probably point out that longer perimeters don't necessarily mean that the object or

01:08

space will be bigger.

01:09

To see that, let's take a look at this pool. [Aerial picture of another swimming pool]

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Like the first pool, this second one has a width of fifteen feet and a length of twenty

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feet…

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…but it also has a weird little square jutting into it, with each side measuring five feet.

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So when we start adding up the lengths of the sides, we again need to add the two lengths

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and one width…

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…but this time we have to add all of those little five foot lengths that make up the

01:30

other side.

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So this pool has a perimeter of 80 ft., which is longer than the first pool's perimeter, [Coop pointing at a blackboard]

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even though it has less space inside.

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That means that having a really long perimeter doesn't necessarily mean you'll have a better [Family in a pool]

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pool party.

01:43

Who cares if you're in a pool with a perimeter of a hundred feet if you can barely move? [Man inside a paddling pool the shape of a duck]

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