https://content.shmoop.com/contentMachine/edit2.php?id=F827B21556284FDDB431D7AC7C223D4F&class=SHVideo

3rd Grade | Math |

Elementary and Middle School | 3rd Grade |

Language | English Language |

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

What's the concept of perimeter?

We're glad you asked!

…No seriously.

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

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

So let's take a look at this pool.

And for now let's only look.

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

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]

its four sides…

…and then add them all together.

So let's do it.

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

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

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

…to one width…

…to the other length…

…and to the other width…

…which gives us the grand total of seventy feet.

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

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

space will be bigger.

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

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

feet…

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

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

and one width…

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

other side.

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

even though it has less space inside.

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

pool party.

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]