ShmoopTube

00:03

[Dino and Coop singing]

00:13

Meet Fern.

00:14

Fern's favorite food is pizza. [Fern sat at a table with a pizza slice]

00:17

Fern’s birthday is coming up and her best friend Amelia wants to surprise Fern with

00:21

what she thinks is an awesome gift: [Amelia sat with a wrapped present]

00:22

A pizza the size of a lunchroom table.

00:25

Ya know, Amelia dreams big and we like that about her. [Amelia stick her arms in the air and looks excited]

00:29

But if any of you are watching this and are thinking, what a great idea for a birthday present...

00:33

Stop thinking that immediately.

00:34

Never get anyone a table sized pizza, it's a dumb idea.

00:37

Well it is, anyway... back to the video. [Table of pizza falls to pieces]

00:40

To make her dumb plan work, and to make sure she gets just the right amount of dough, cheese and sauce

00:45

Amelia's gonna need to know the area of the tabletop. And Amelia's in luck because guess what... [Amelia mixing ingredients]

00:50

There's a formula for that.

00:51

If you need to know the area of a rectangle like, say,

00:54

a lunch table…

00:55

All you need to remember is that “Area” equals “Length” times “Width.”

00:58

So, if the table is 4-meters long and 2-meters wide… [Drawing of the table]

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… we just plug those numbers into our formula…

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… and see that 4-meters times 2-meters equals 8-meters squared.

01:07

Oh

01:08

And there’s one important detail to keep in mind when calculating area: Since we’re

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multiplying measurements, our result will always be squared.

01:16

Just for fun, though, what if Amelia knew the area of the table, the length of the table, [The width of the table is rubbed out by an eraser]

01:20

but, for some reason, she didn’t know the width of the table?

01:23

No need to panic, because our previous formula can help us find a mysterious variable, too.

01:27

Not that you were panicking... Really, this is a pretty low stake scenario [Amelia puts a pizza into the oven]

01:31

We don't even know why Amelia's doing this...

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We're just kinda going along for the ride... [Amelia walks out the kitchen]

01:35

So to find our mystery variable

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We just have to work backwards.

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First, we plug in what we know about the equation.

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Then, we isolate our variable by dividing, always remembering that what we do to one

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side of the equation, we have to do to the other side, as well.

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In this instance, we’ll divide both sides by four meters.

01:51

What we’re left with is our missing variable: two meters. [The answer is written in red]

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And now Amelia knows exactly how big a pizza she needs to make.

01:58

Though did she consider how hard it would be to toss an 8-meters-squared [The dough lands on Amelia's face]

02:01

piece of dough…

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Or how she'd gift wrap a table sized pizza...

02:05

No, she didn't... Good job Amelia. Maybe next time stick to a gift card. [Amelia drops the giant pizza onto the floor]

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