Ironically, it all started with a math puzzle. The next thing I knew, the newest member of our club had disappeared. It has been three days since we’ve seen or heard anything from her, and now it’s time for the Math Kids to do something about it. But I’m getting ahead of myself, so I’ll begin at the beginning…

It was Friday, and we had almost made it through another week with Mrs. Gouche. She was our fourth-grade teacher and wasn’t too bad most of the time. I liked that she had separate math groups so we wouldn’t get stuck doing the easy math with Robbie Colson and Sniffy Brown. Sniffy’s real name is Brian, but everyone called him Sniffy because he always has a runny nose and sniffs loudly. We never call him Sniffy to his face, of course. He is friends with Robbie, Bill Cape and Bryce Bookerman, the class bullies.

“Don’t forget that we have Math Kids Club tomorrow,” I reminded Stephanie on the way into class.

I’m the president of The Math Kids club at McNair Elementary School. I wasn’t exactly elected to the position, though. Stephanie Lewis said I should be president since the club was my idea, and Justin Grant, my best friend since kindergarten, didn’t object. There was no need for an election since there were only three of us in the club. I already knew Justin was coming to the meeting because we had talked about possible problems to tackle while we walked to school that morning. Justin had a new book of math puzzles he was planning to bring.

You’re probably thinking that all we do in The Math Kids club is sit around and solve math problems. That was how the club was started, but it sure took a few strange turns along the way. Who would have thought that we could use math to crack a case the police couldn’t solve? Still, the original idea for the club was to solve math problems. And when all the excitement with the burglars was over, trust me, that’s all we wanted to do.

“Wouldn’t miss it, Jordan!” Stephanie said. “No wait! I have soccer practice, so it would have to be after that.”

I rolled my eyes as I took my seat in class. This would take some finessing on my part. Justin and Stephanie had had more than one blow-up over her soccer practices colliding with our math club. But finding a way to avoid another shouting match was a problem I’d face after school. And, surprisingly, the solution didn’t come from me this time.

Mrs. Gouche has been giving our math group tougher and tougher problems as the school year goes on. She knows that Stephanie, Justin, and I are good at math and really like hard problems, so she has made it her mission to really challenge us. Take today’s problem, for example.

“This, my friends, is called The Sixes Problem. Catherine, can you hand this to Jordan?”

The girl who sat in front of me—Catherine something—handed me the problem sheet. I noticed she took a long look at it before passing it back to me. I smiled, knowing that she probably wouldn’t have the first clue on how to solve the kind of problems our teacher had been giving us. Little did I know that she knew a lot more than I thought and would end up being right in the middle of our next mystery.

Mrs. Gouche put her dry marker down and returned to her desk. She had an evil glint in her eye and my heart started to beat a little faster. The problem *looked* simple enough when I first scanned it. We had to use three of the same number, like 2, 2, 2 or 5, 5, 5 and any mathematical operations, like multiplication, division, or addition, or to make 6. For example, to solve for the number 2 we could use 2 x 2 + 2 = 6. It didn’t look difficult, but it turned out to be much tougher than we thought!

We went to the white board and started working. We easily came up answers for the numbers 2 and 6.

2 + 2 + 2 = 6

6 + 6 – 6 = 6.

The problem was that we had to do the same thing with all the numbers from 0 to 9.

While the rest of the class was working on their social studies homework, the three of us stood at the whiteboard, dry erase markers in our hands as we tried to solve for all the numbers.

Justin got us the next two answers when he remembered that any number divided by itself is just one. That means that 5/5 is just 1 so we could use 5 + 5/5 = 6. We used the same trick to solve for seven.

That meant we had four down and six to go.

0)

1)

2) 2 + 2 + 2 = 6

3)

4)

5) 5 + 5/5 = 6

6) 6 + 6 – 6 = 6

7) 7 – 7/7 = 6

8)

9)

Zero and one looked impossible. They might really be impossible, too. We had lost a class pizza party when Stephanie bet Mrs. Gouche that we would solve a problem called the Bridges of Königsberg. It turned out the problem didn’t have an answer. Score one for Mrs. Gouche!

“I don’t think there are answers for zero and one,” Justin complained.

“Me, either,” I added. “Let’s work on three and four. I’m sure we can get those.”

Three turned out to be pretty easy:

(3 x 3) – 3 = 6.

We were halfway there!

And halfway there was all the further we got. We stared at the board and made some attempts at new ideas, but the last five answers remained out of our reach. The three o’clock dismissal bell rang while we were still staring at the board.

“We did pretty well, Mrs. Gouche,” I announced. “We’ve only got three more to go.”

She glanced up at the board.

“It looks like five more to go,” she said. “Did you forget about zero and one?” she asked, turning her focus back to the papers she was grading.

“But those are impossible,” I protested. “You were trying to trick us again.”

“No tricks this time,” she said. “There are answers for every number from zero to nine.”

We stared at the remaining problems on the board. *There was no way we could do anything to get three ones to somehow equal six. And the zeros? Forget about it.*

The class started to gather up their papers and books and stuff them into backpacks. Robbie and his buddies pushed each other as they rushed to get out of the room. None of the bullies had detention for a change, so they were anxious to get out to the playground for a game of soccer. We are on temporary good terms with the bullies. I don’t know how long it will last, but at least for now I don’t have to worry about them knocking my backpack on the floor or tripping me as I walk past them or threatening to rearrange my face at recess. We had Stephanie to thank for that. It was her idea to have Robbie’s dad help us catch the burglars. Mr. Colson is a policeman, but usually doesn’t do anything more exciting than writing parking tickets. When we used our math skills to figure out when and where the burglars were going to hit next, Stephanie found a way for Mr. Colson to get credit for cracking the case. Robbie’s dad is happy, which means we are on Robbie’s good side—for now.

“Well, I guess I know what we’ll be working on in the Math Kids Club tomorrow,” I said sadly.

Normally, I would be happy to work on a tough math problem, but I knew there was no way we were going to be able to solve this one.

“Let’s start early tomorrow,” Justin said. “We could meet at—”

“I’ve got soccer practice,” Stephanie interrupted.

“Of course you do,” Justin replied sarcastically. “The sun is up so you must have soccer practice.”

Stephanie gave him an irritated look as she tugged on her ponytail. Wanting to avoid an argument, I jumped in quickly. “How about Justin and I get started and you come over after practice?” I asked.

“Yeah, that would work,” she said.

“It doesn’t really matter,” Justin sulked. “We’re never going to get answers for zero and one anyway.”

“Factorials,” said a small voice near the door.

“What did you say?” asked Justin.

“Factorials,” repeated the small voice, which we now could see had come out of the mouth of the girl who sat in front of me, Catherine… Duchesne, I knew I’d remember her last name. “You need to use factorials to solve for zero and one.”

“How is a factory going to help us solve a math problem?” I asked.

“Not a factory,” she laughed. “Factorials.”

And with that, she was out of the room and mixing with the crowd of students headed down the hallway to the exits.

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