The Tooth Fairy Math

Theo was the kind of kid who could not let a thing go.

If you told him the sky was blue, he'd ask, "But what kind of blue?" If you told him dinner was at six, he'd ask, "Six o'clock where? Here or in Japan?" His brain was like a hamster wheel that never, ever stopped spinning.

So when Theo lost his very first tooth — a tiny bottom one that had been wiggling for three whole weeks — he didn't just put it under his pillow and go to sleep like a normal person.

He went to find Mae.

Mae was ten. She was reading on her bed with her feet up on the wall, which their mom said would leave scuff marks but Mae did it anyway. She had already lost eleven teeth, so Theo figured she was basically an expert.

"Mae," Theo said, standing in her doorway. He held up the tooth between his thumb and pointer finger. It was so small it looked like a grain of rice wearing a tiny hat.

"Nice," Mae said, not looking up from her book.

"Mae. I have questions."

Mae sighed. She dog-eared her page. She knew from experience that Theo's questions were never just one question. They came in packs, like wolves.

"Go ahead," she said.

Theo sat cross-legged on the floor. "Okay. So the Tooth Fairy comes tonight, right?"

"Right."

"And she takes the tooth."

"Yep."

"And she leaves money."

"Usually a dollar. Sometimes two if it's a really good tooth."

Theo examined his tooth carefully. "How would she know if it's a good tooth?"

Mae thought about this. "Probably no cavities. Clean. Maybe she has a little magnifying glass."

Theo nodded. That made sense. Then the hamster wheel started spinning faster.

"How does she get in the house?"

"Same way as Santa, probably. Magic."

"Through the chimney? We don't have a chimney."

"Magic doesn't need a chimney, Theo. That's the whole point of magic."

"Okay, fine. But how does she know I lost a tooth today? Does someone tell her? Is there a phone number? Does she have an app?"

Mae put her book all the way down now. She sat up. This was going to be a long one.

"I think she just… knows," Mae said. "Like how dogs know when a storm is coming. She can sense it."

"She can sense my tooth fall out? From wherever she lives?"

"She's magic, Theo."

"Where does she live?"

"I don't know. Somewhere sparkly."

"Like a cloud?"

"Sure. Like a cloud."

Theo was quiet for a moment. Mae almost picked her book back up. Almost.

"Mae," Theo said. "How big is the Tooth Fairy?"

"Small. Like, really small. Like the size of your hand."

"That's what I thought," Theo said, and his eyes got that look — the look that meant the hamster was absolutely sprinting now. "So she's the size of my hand. And she carries a tooth — which is basically as big as she is — plus she carries money. Coins or dollar bills?"

"Dollar bills."

"A dollar bill is bigger than her, Mae. That's like me carrying a mattress."

Mae blinked. She had never thought about this before.

"Maybe she has a bag," she said. "Like Santa."

"How big is the bag? Because here's the thing." Theo stood up. He started pacing. "There are billions and billions of people in the world."

"Not all of them are losing teeth tonight."

"Okay, fine. But kids start losing teeth around six. And they stop around twelve. That's six years of teeth. And every kid has twenty baby teeth."

Mae stared at him. "How do you know that?"

"I looked it up. After lunch. When the tooth fell out."

Of course he did.

Theo kept going. "So there are maybe a billion kids in the world who are the right age to be losing teeth. And each one loses twenty teeth over six years. So every single night, there could be millions of teeth being lost."

"Millions?" Mae said.

"MILLIONS, Mae."

They looked at each other.

"There's no way one fairy does all that," Theo said. "Not if she's the size of a hand."

Mae chewed her lip. "Maybe there's more than one."

"How many?"

"I don't know. A lot. Like, a whole army of tooth fairies."

"An ARMY?"

"A nice army! With sparkles and wings. Not a scary army."

Theo sat back down. He stared at his tiny tooth. "Okay. So there's an army of tooth fairies. And they all fly around every single night, going into millions of houses, finding millions of pillows, carrying teeth that are basically the size of their whole bodies, and also carrying dollar bills that are bigger than they are, and they do all of this while kids are sleeping without waking anyone up."

Mae nodded slowly. "That's the deal."

"That's a LOT of work."

"Yeah. It really is."

Theo frowned. Something was still bothering him. Mae could see it. The hamster wheel was squeaking.

"What?" she said.

"Okay, here's the real problem," Theo said. He held up his tooth again. "She takes the teeth."

"Right."

"Millions of teeth. Every night."

"We covered this."

"Mae. What does she do with all the teeth?"

Silence.

Mae opened her mouth. Then she closed it.

"Because that's… that's a LOT of teeth," Theo continued. "Even if it's an army of fairies. Where do the teeth GO? Does she build something? Does she collect them like stamps? Does she have a warehouse? A TOOTH WAREHOUSE?"

Mae felt her own brain start to spin. "Maybe she—"

"And if she's been doing this FOREVER — like, for hundreds of years — then she has BILLIONS of teeth, Mae. BILLIONS. That's not a warehouse. That's a whole tooth PLANET."

Mae stood up. She walked to her window and looked outside, like the answer might be sitting in the backyard next to the swing set. It wasn't.

"Maybe," Mae said slowly, turning back around, "she makes something out of them."

"Like what?"

"Like…" Mae looked up at the sky through the window. It was getting dark. The first stars were beginning to appear, tiny and white and softly glowing. She stared at them for a long time.

"I don't know," she finally said. "I really don't know."

They both sat there, Theo on the floor, Mae by the window, thinking about billions of tiny white teeth and what in the world you could possibly do with all of them.

Finally, Theo broke the silence. "You know what? I'm putting the tooth under my pillow."

"Yeah?"

"Yeah. And I'm gonna try really hard to stay awake so I can ask her."

Mae smiled. "You won't stay awake. Nobody ever stays awake."

"I will."

"You won't."

"I WILL."

He wouldn't.

The next morning, Theo came running into Mae's room at six-fifteen, which was way too early, but Mae could see on his face that she wasn't allowed to be mad about it.

"I fell asleep," he said.

"I know."

"The tooth is gone."

"I know."

"There's two dollars. TWO. So it must've been a really good tooth."

"Told you. No cavities."

Theo climbed up onto the end of her bed. He was quiet for a second. Mae waited. She knew there was more.

"Mae?"

"Yeah?"

"I don't know what she does with all the teeth. I didn't figure it out. And I didn't get to ask her."

"That's okay."

Theo looked at the two dollars in his hand, then back at Mae. He grinned — and the gap where the tooth used to be made his whole smile look like a little piano with one key missing.

"I've got nineteen more chances to find out," he said.

Mae laughed. She really, truly laughed.

"Yeah, Theo," she said. "You do."