ShmoopTube

00:04

Two-Step Equations Using Multiplication and Division , a la Shmoop.

00:12

After returning from vacation, Dr. Villain comes home to find he has only one laser-shark

00:17

left.

00:18

His man-servant, Bill, explains that the first half were killed by flesh-eating bacteria.

00:24

And then he ate another three because he'd forgotten to go grocery shopping.

00:34

Can you determine how many sharks Dr. Villain had before his Jamaican getaway?

00:41

As always, we'd like to have a formula to help us solve the problem.

00:45

So we first need to determine the variable.

00:49

Because we're trying to figure out the original number of sharks, we're going to substitute

00:53

that value with x. In the beginning, there were x number of sharks.

00:59

Then half were eaten by flesh-eating bacteria. We'll write that as x over 2.

01:03

Guess someone should have washed their hands a little better.

01:11

Then Bill ate three of the sharks, so we'll subtract 3.

01:15

We know there was only one shark left, so we can put 1 to the right of the equals sign.

01:21

Our goal is to get x all by itself on one side. So let's first get rid of that pesky

01:26

-3.

01:27

We can do that by using the opposite operation and adding 3 to both sides.

01:34

Remember to always perform the same operation on both sides; Dr. Villain is fair that way.

01:40

Now we have x divided by 2 equals 4.

01:44

While we can't undo the near-extinction of the laser-shark, we can undo x being divided

01:49

by 2... by multiplying 2 to both sides. And there you have it, Villains and Man-Servants:

01:57

x equals 8.

02:01

Which means the original number of laser-sharks totaled 8.

02:06

Hey there, turn that frown upside down, Dr. Villain.

02:11

You may only have one laser-shark left. But even a sad, friendless laser-shark is still

02:16

a laser shark!

02:20

Just remember that, in the future, you might want to hire better help...preferably someone

02:24

who doesn't have a taste for laser shark.

Full Transcript