Lu Guo Helps: The Quirky Math of Odd Elementary School (Grades 1--2)

Hidden in a quaint old neighborhood is a quirky elementary school. Lu Guo， who had just graduated from primary school， walked into the “mysterious research institute” disguised as a convenience store at the school gate， and unexpectedly turned back into a first-year freshman. Now he is the best student in the class， and when his classmates have difficulties， they always ask Lu Guo for help. He can always easily resolve disputes.

The “Daring Professor” in the Convenience Store

If Lu Guo had known that picking up that colorful bouncy ball would lead to such strange events， he wouldn’t have taken the ball at all.

Lu Guo had just graduated from sixth grade and planned to visit the convenience store near the school one last time. This store was very popular with students， often bringing in new and interesting items， and with the enthusiastic recommendations from the store owner， each time he visited home， he ended up spending an extra fifteen minutes. In the store owner’s words， “Passers-by， don’t miss out. Come browse for a quarter of an hour， and you’ll leave feeling much better.”

The store owner treated the students very well. No matter how much they spent， he would always cheerfully exclaim， “Thank you， thank you! What a big purchase!” Also， because he was quite thin， the students nicknamed him “Daring Professor，” which was homophonic with “big purchase and slim” in Chinese but sounded impressive.

Lu Guo had his eye on a colorful bouncy ball and paid the Daring Professor， who was busy organizing goods. Just as he stuffed the ball into his pocket， he felt something bump against his foot. Looking down， he saw the ball rolling out of his pant leg and into the back room of the store.

Originally， there was one ball in his pocket， but after losing one， how many were left? The answer is zero. Because there was nothing left.

This math problem immediately popped into Lu Guo’s head. He reached into his pocket only to discover his answer was wrong. There was still a big hole in his pocket.

There was a beaded curtain at the back-room entrance， made of colorful beads. Lu Guo thought the curtain resembled a color-blindness test， as there were two vaguely visible symbols on it: “--” and “six.”

Seeing the ball roll inside， Lu Guo didn’t hesitate to lift the beaded curtain and dart in. Just as he did， the curtain fell down with a rustle. The beads jumped and scattered all over the floor. Lu Guo recalled the line from a poem learned in Chinese class: “White rain bounces off beads， disturbing the boat，” along with a lesson from science class: If you step on the beads， friction decreases， and you might end up landing on your butt.

Lu Guo’s right hand seemed to press down on something， and looking down， he saw it was the bouncy ball.

He stood up straight， brushed off the dust from his knees， and when he looked up， he found the Daring Professor standing right in front of him.

The Daring Professor looked a bit different; his outfit had changed from work clothes to a trench coat， his hair was slightly gray， and he had even added a pair of glasses -- he truly looked like a professor now.

“Oh dear， how did you end up in this ‘Magic Number Laboratory?’ Me， your Daring Professor， along with this ‘Mysterious Research Institute’ disguised as a convenience store， have finally been exposed today.”

“Daring Professor， what happened?”

The professor anxiously grabbed Lu Guo’s hands， checking them while muttering， “Oh no， where have you lost six? You still have all ten fingers， and with both hands and feet combined， that only makes four， not enough to lose. Hmm? Did you lose six hairs? Now that would be impossible to count…”

Lu Guo found it quite amusing. “I didn’t lose anything; I feel completely normal， if not more…”

Looking down， he was stunned to see that his sleeves and pant legs had all grown significantly longer. When he glanced into the mirror in front of him， he realized he had transformed into an elementary school student， not just any student， but one who had just entered first grade!

Teacher Star Can Organize Lines

The Daring Professor rubbed his hands together， exclaiming， “Oh no! It turns out your grade has been reduced by six. You， who just graduated from sixth grade， are going to attend elementary school all over again!”

“Then hurry up and change me back!” Lu Guo didn’t want to spend another six years being a pupil. He crouched down to search for the beads， but some had already fallen into the drain. How could he possibly find them all? Even if he did， how could he reconstruct the original pattern of “--6”? Besides， wouldn’t it be “+6” this time? Because if a first grader lost another six years， they might end up as a newborn baby! Now he had no way to return.

The Daring Professor said apologetically， “Don’t worry. There’s still a version of you in the original timeline. Just stay in this world for now. When you need help， come find me at the convenience store. That colorful bouncy ball can also assist you.”

Lu Guo felt a bit dazed as he walked towards the school with his slightly oversized backpack. Although the school was in the same location， a new sign now hung at the entrance that read “Quirky Elementary School.” The surrounding community had taken on an antique charm， almost like it was in a tourist area.

As dawn broke， two security guards were busy opening the gates. A young teacher with a ponytail ran over and asked the man at the entrance， “Principal Smile， can my Class 1A have one more student? That way， we’ll have exactly 24.”

Principal Smile， always smiling， replied， “Why must it be 24 students?”

“24 is a great number! It can be counted in pairs of 2， triplets of 3， groups of 4， and sets of 6... It just works out perfectly.”

“You， a math major， are putting all these principles into class management，” Principal Smile said， scratching his nearly bald head， worried about where to find a new student.

Lu Guo stepped forward and greeted Principal Smile， “Hello， Principal. Since I’m now a first grader， which class should I join?”

“That’s great! It’s a perfect match. There’s a class missing a student， and here’s a student looking for a class. You can join Teacher Star’s Class 1A.”

And so， Lu Guo， who had completed elementary school， became a student in Class 1A again.

Teacher Star was a new teacher， fresh out of college， and she wasn’t very experienced in managing students. The school had assigned her an experienced mentor， the short-statured math teacher from Class B， Teacher Dan. However， Lu Guo felt that Teacher Star was managing the class quite well.

A week later， the first graders gathered on the playground. Some classes formed long lines， others wide rectangles， but all were rectangular shapes. Only Class 1A managed to form four triangles， their points aligned， making it look like a lucky clover.

Lu Guo felt very happy. He thought that repeating first grade was actually a good thing， as many things had changed. Well， except for his parents， who remained the same.

Lu Shengyi

Lu Shengyi is a writer of mathematical fairy tales， a senior primary school mathematics teacher， and a full-time teaching and research staff. He has taught provincial and municipal open courses many times and presided over a number of provincial and municipal research projects.