It's me Ding Sauce.

Today we're going to enjoy a little bit of MMM, Michael's Math Magic.

Thirteen years ago I discovered this pillowcase in a graveyard in Cincinnati and I could have

sworn it was smiling at me.

It was so weird.

I was like “Wipe that grin off your face pillowcase.” and it was like “No, how

about that?

I'm not going to do what you say because I am the Pillowcase of Terror.”

And I was like “okay that sounds pretty bad.

I'm gonna leave.”

and it was like “No no no sorry it's just the name my parents gave me.

I'm actually pretty nice.

Really all I do is take that which is out of balance and I make it equal.”

And I was like okay yeah sure but if you say it that way it still sounds scary.

Anyway long story short we became friends but it is after all the Pillowcase of Terror

so I have to keep it locked up.

But if we're quiet enough we should be able to let it out.

Hannah could you make sure the door is locked.

Yeah.

Okay everyone hold your breath.

Don't let it know you're living until I have it in my hands.

Okay.

We're good?

Okay.

The Pillowcase of Terror.

Let me show you one of the things that it does.

It freaked me out when I learned it so here's a deck of card.

Nice bid ol' cards.

Boom.

Nice and big.

I'm gonna put these in the Pillowcase of Terror and I'm gonna meditate on my greatest

fear.

That which I wouldn't wish upon even my worst enemies.

Look at that.

Now the first time this happened to me I was like “That is amazing” and the pillowcase

was like “These small cards were always inside me you just put the big ones in and

then you let go of them and you picked up the small ones.”

I was like “Ahh you're right.”

Okay so that wasn't magic.

But today we're gonna do some real magic and this will defy reason so to protect us

I'm gonna be using my Greek philosopher playing cards.

You could really use any deck you want but this one makes me feel safe.

Now the power of the Pillowcase of Terror is a little bit frightening to me honestly.

But I think we might be able to outsmart it today.

Let's see.

Hannah what's your favorite number?

6.

6, okay.

1, 2, 3, 4, 5, 6.

And uhh Jack what's your favorite number?

5.

5?

Okay.

1, 2, 3, 4, 5.

6+5 is 11 so we have an odd number of cards here.

That's good.

I like that.

Here's how we're gonna test the pillowcase.

I'm gonna take the 11 cards and turn them face up so now we have 11 face-up cards.

Easy, great, perfect.

Now I'm gonna shuffle these face-up cards into the rest of the cards which are face-down.

Perfect.

Okay.

Push them together.

Let's give them a few little moves like this.

I'll do a little riffle and then a little cascadey-dude.

Beautiful.

Great.

Okay so we now have a shuffled deck of a card, 11 of which are face-up.

And there those face-up cards are sort of randomly distributed throughout the deck.

What I'm gonna do now is take this deck of cards and I'm going to put it in my hands

inside the pillowcase of terror.

It won't be pretty but when I am done, and the pillowcase is done and I take my hands

out I will be holding out two piles of cards.

They may not have the same number in them, I don't know but what I do know is that

the number of face-up cards in both piles will be equal.

Ready?

Ohhh!

Okay they're getting really hot!

Okay!

It's done!

It's happened.

I now have two piles of cards.

They're not of equal size but they should have the same number of face-up cards each.

Let's see if the case has done its work.

Okay.

In this pile we have 1, 2, 3, 4, 5, 6, 7 face-up cards.

In this pile we have 1, 2, 3, 4, 5, 6, 7 face-up cards.

7 face-up cards in both piles.

That's why they call it the Pillowcase of Terror.

Okay so how does this trick work?

Well believe it or not this is just a regular old pillowcase.

There's nothing special about it.

Fooled you right?

You don't need to be scared of it and it has no magical powers.

This trick is self-working.

It's math magic.

As long as you follow the right procedure you will always get the result that you want.

All you have to do is count out some number of cards.

Let's say seventeen.

1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17.

Now I'm gonna flip these cards over and they're now face-up.

When I shuffle them into the deck it really does not matter where they go.

You could even have a friend do this.

You could have some member of your audience do this.

We really just wanna mix them all around.

And there's no trick involved into where they go.

We just wanna have those 17 face-up cards in the deck somewhere.

Doesn't matter where they are.

Then you take seventeen cards out of the deck.

Doesn't matter from where but it's easiest to take them right off the top.

1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17.

Now what I do is I take the 17 I took off the top and I flip them over and boom both

piles now have the exact same number of face-up cards every time.

For real let's take a look.

This pile has 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12 and this pile will also have 12.

Watch.

1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12.

How does this work?

It's actually quite simple.

When I take some cards out of the deck.

Let's say 24 in this case.

Here's 24 cards.

I take out 24 cards and I turn them over.

I now have 24 face-up cards.

I shuffle them into the deck.

There are 24 face-up cards in the deck.

Could be any number of cards though.

There we go.

24 cards are now face-up in this deck.

I then remove that number of cards from the deck from the top for example.

1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24.

Perfect.

Now what do we know.

We know that there are a total of 24 face-up cards all together.

We also know there are 24 cards here.

So how many face-up cards are here?

We'll call this Pile A. And we'll call this one pile B. In pile A, how many cards

are face up?

I don't know!

I shuffled them.

It's all kind of random.

I didn't pay attention to where I put them.

Let's just call that number X. Okay.

So in this piles of 24 cards, x of them are face-up.

So how many are face-down?

Just 24-X.

Now how many cards in this pile are face-up?

Well, we know that there's 24 face-up cards total.

And x of them are in here.

So the number of face-up cards in this pile, Pile B, is 24 minus the x that are in here

so we have 24-x face-up cards here and we have 24-x face-down cards here.

When I turn one of the piles over.

Doesn't actually matter which one every face-up card becomes the opposite, face-down.

And every face-down card becomes faced-up so we have the same number of face-down cards

in A as we did face-up cards in B. I just changed all of those face-down cards to face-up

cards so now we have the same number of face-up cards in both piles.

Interestingly you can choose to reverse either half so long as you don't reverse both of

them and that is the trick of the Pillowcase of Terror.

Also known as cards in the dark.

Missmag himself didn't even give it a name.

He just did it and it's amazing.

But I love the trick and it's really fun to use these sort of concepts and mathematical

principles to develop your own magic.

So have fun, keep your pillowcases locked up, and as always, thanks for watching.