Translator: Dreamscribe
The second round of the Korean Mathematical Olympiad is held at KAIST.
I was worried that I might have to go to Seoul, but fortunately, test centers were arranged in each province.
It’s not that I hate Seoul, but the traffic is terrible and the air is bad, so every ti I go, I feel stifled.
“I’ll do well and co back.”
“Okay, call after it’s over!”
The area near the university’s main gate was too crowded, so I got off beforehand.
After sending off Dad, I trudged along the path.
Because Mom was cooking from early dawn, I woke up early too. The exam consists of six questions. It’s divided into two sessions of two hours and thirty minutes each. Of course, there’s a lunch break in between.
‘She really didn’t have to do all this…’
I feel a bit embarrassed holding the thermal lunchbox in my hand.
Still, since it’s probably packed with delicious food, I’m looking forward to lunch.
As I walked along the path, I saw a pond.
“Duck pond?”
What a half-hearted na.
As I approached, I saw many ducks lazily floating on the water. I blankly stared at them for a while.
Gentle eyes and wide yellow bills.
Soft and warm feathers and bodies sleekly shaped for fluid dynamics.
Unlike chickens, ducks even know how to share food with each other.
And on top of that, they waddle cutely.
‘Even their toes are cute.’
Most of all, the fact that all of this is a harmony created by natural selection is fascinating.
Since the days I devoured the Encyclopedia Collection, I’ve always liked ducks.
‘I wonder if there are any souvenirs?’
I hurried to the store and found it full of silly-looking blue plushies.
As I kept looking, they started to seem oddly cute, so I bought one along with so duck rchandise.
‘I’ll give it to Seo-eun.’
“Ah!”
Without realizing it, I’d been completely absorbed in the ducks.
I could almost hear my teacher’s nagging. He reminded several tis before the exam.
“Don’t expect the grader to understand everything you write. They have to grade answers from over 200 students, do you think the professors handle all that? So of the TAs are really stupid, so make sure you rember, okay?
When writing answers, how are you supposed to write them?”
“In a simple, easy-to-understand way.”
“Right. Even if your brain skips steps automatically, your answer shouldn’t, got it?”
He lectured so much I could practically grow calluses on my ears.
Hurriedly.
My pace quickened as I headed to the lecture hall.
I arrived at the Natural Sciences Building and found the test room.
Creak.
When I opened the door and went in, I saw many familiar faces.
“Yu Seo-ha! I knew you’d co too.”
Lim Su-jeong noona, who was sitting quietly in one corner, raised her hand cheerfully.
It's embarrassing. I deliberately avoided her gaze and searched for my assigned seat as written on my exam slip.
"That's him, right?"
“Is an elentary school student really allowed to compete in the IMO?” (TL: IMO = International Mathematical Olympiad)
“It’s happened abroad. I heard Elijah Cronen started competing when he was ten.”
I’ve gotten used to the murmuring now.
I want to be an adult quickly. Even just a few years older would be enough.
A group of students, probably friends, gathered and intentionally spoke loudly.
Ah! I rember reading about this in the Encyclopedia Collection.
Social safety net, conformity pressure, symbolic display.
A behavior ant to gain psychological stability by forming a clique in an unfamiliar environnt.
They’re all anxious.
Thinking that made them not seem so bad anymore.
One of the bigger students pointed at soone and asked,
“Hey! Choi Yoo-jin. Looks like you’re not the youngest anymore?”
“Hyung! Did you think I’d stay an elentary schooler forever?”
An irritated voice.
If I’d known it would be like this, I should’ve spent more ti in the souvenir shop.
“Why don’t you go and say hi? You guys are going to see each other a lot from now on, right?”
“Ugh, so annoying.”
Step, step.
Until now, when I went to test centers, people pretended not to see .
So although it was uncomfortable, it didn’t really affect the exam itself. But this place had a completely different atmosphere.
‘It’s like an inner circle?’
They definitely feel a certain level of camaraderie toward .
But why?
At best, we might have crossed paths once or twice.
“Hey, Yu Seo-ha!”
Choi Yoo-jin called out to . I couldn’t pretend not to hear him now.
“Yes?”
“You’re in 5th grade, right? Where are you from?”
Why the sudden background check?
I felt a bit rebellious, but my body was honest. Because older kids are scary.
“Okcheon County, Chungbuk.”
“No, not that co on, you know what I an!”
He yelled, sounding frustrated.
My shoulders shrank.
“D-Dodam Elentary School?”
Only then did he seem to realize sothing was off.
“What? You’re not from the Gifted Education Institute?”
“No, I’m not.”
He laughed in disbelief.
“Wow! This guy’s hilarious. You ca here at that age without even being from the Gifted Education Institute? I’ve never even heard of sothing like this.”
“Is it strange?”
“Of course, it’s strange. All the middle schoolers here ca from the sa Gifted Education Institute. Even Su-jeong noona over there.”
I had no idea.
I glanced back and saw Lim Su-jeong noona shrug her shoulders.
“Anyway, I’ll take good care of you from now on. I was the first place winner in the Seoul National University competition, so you’ll pass the second round, right? Just trust . I’ll let you join our study group. That’s super helpful, you know? We don’t just let anyone in, okay? I’ve been the youngest until now, but finally, soone younger has joined under .”
Joined what, exactly?
And when did we get close enough for him to call himself my hyung?
Unlike his earlier attitude, where he clearly showed he didn’t like , he was now incredibly talkative.
“Yes, thank you.”
I couldn’t think of anything else to say, so I bowed politely.
He patted my shoulder, seemingly satisfied.
Creak.
“Everyone’s here, right? Let’s begin the exam.”
When the proctors ca in, the lecture hall quieted down.
A woman wearing glasses and a scruffy-looking young man.
They were an oddly fitting pair.
Rustle.
The bell rang, and the exam papers were distributed.
Now it was entirely my own ti.
Problem 1.
[In a party with 6 people, show that no matter which 3 people are chosen, there will always be a group of 3 who either all know each other or all don’t know each other.]
A classic Ramsey theory question using the pigeonhole principle.
Scratch, scratch.
The morning session’s problems mostly seed focused on evaluating depth of thought.
‘Do I really need 2 hours and 30 minutes for this?’
Rembering my teacher’s advice, I took my ti and tried to write out in-depth explanations.
“... therefore, in any case, a group of 3 that ets the condition must exist.”
Problem 2.
[Show that among 1,000 consecutive natural numbers, there is always at least one composite number.]
It's a number theory problem.
Seeing a question related to pri numbers made smile.
Lately, Seo-eun has been enjoying number gas so much that I think she’s morized all the pris under 500. She might get bored, so from now on I should play with her by starting from 1,000 and going downward.
Scratch, scratch.
“... therefore, 1001! k is divisible by k and thus is a composite number. In this way, 1,000 consecutive composite numbers can be constructed.”
Problem 3 was about planetary orbits that I used to see on the wall when I was young.
When I closed my eyes, a beautiful universe unfolded.
The beauty of elliptical orbits expressed in polar coordinates. They have two foci, but the sum of the distances from a planet to the two foci always remains constant.
The complex motions of the solar system’s planets governed by such simple mathematical rules.
A perfectly ordered cosmos without a single error.
How happy must Kepler have been when he figured this out through calculation?
I want to experience that kind of joy too.
It was a problem clearly intended to challenge our thinking, but it wasn’t difficult if you had a good understanding of celestial motion.
Beep-
“Stop! Submit your answer sheets and then have lunch.”
As soon as the proctors left, voices started popping up all over.
“Hey, wasn’t number 3 way too hard?”
“I ssed up starting from number 2.”
“Is number 3 for real? Isn’t that graduate school level?”
Slide.
I quietly stood up, holding my lunchbox.
It’s winter, so it’s tough to eat outside, where should I go?
Then a voice ca from behind.
“Hey!”
Lim Su-jeong noona?
She called out to with her arms crossed and a sulky expression.
“Yes?”
“Let’s eat together. You don’t know anyone else here anyway, right?”
“Thank you.”
I obediently followed her.
I didn’t know the layout of the place, and there wasn’t really a good spot to eat alone nearby.
We arrived at the cafeteria on the first floor.
I sat down and placed the thermal lunchbox I brought on the table.
“Pfft- You really are a kid.”
I was already self-conscious about it...
As soon as Su-jeong saw the colorful character lunchbox, she burst out laughing.
My face turned red. I should pass it down to my little sister from now on.
“When I was at the Gifted Education Institute, my dad used to pack lunch a lot too. I miss it.”
She had a wistful look on her face.
“What are you going to eat, noona?”
“I’m going to buy sothing over there.”
When I turned my head, I saw the food court selling a variety of als.
While I was opening my lunchbox and waiting, that sa group approached. I quickly turned my head, but they seed to be heading straight toward .
“Yu Seo-ha! Why’d you run off so fast? Let’s eat together.”
Thud.
In an instant, three of them gathered and placed their trays around .
I should have told them soone was sitting here, but they had already picked up their spoons and started eating.
“Hey! Why are you guys here again?”
As expected, Su-jeong ca over from behind, looking angry.
"Let's eat together. He's alone too. It's been a while, Lim Su-jeong. Is the Gifted School treating you well?"
"I don't know!"
Maybe they used to be close. The big guy offered her a seat next to him. But she didn’t like that and walked around to sit beside instead.
Everyone seed hungry and began eating.
“This is good.”
“Way better than our school als.”
“But did you solve number 3?”
“Our teacher said that question 3 from the first session and question 6 from the second aren’t ant to be solved completely. Just finding an approach can still score high.”
“Yeah, I heard that too.”
“I think I solved it properly, though?”
The big guy let out a small laugh, then pulled out his notebook and wrote down the problem.
He looked at and asked.
“Hey! Yu Seo-ha. You haven’t learned this yet, have you?
My dad’s a university professor, and he told that to solve this problem, you need to know celestial chanics and orbital chanics. It’s from aerospace engineering…”
He pulled closer.
As he glanced sideways, it was clear he was watching Lim Su-jeong, conscious of her presence.
“Lim Su-jeong, did you solve this?”
“No. I just wrote down so assumptions.”
“Then listen too. So these six orbital elents are…”
“Wait a minute!”
Just as he was about to write down his solution and explain orbital chanics, noona cut him off. Then she looked at .
“Yu Seo-ha, be honest. You got this one right, didn’t you?”
Why was she doing this to ?
But I couldn’t lie and say I got it wrong.
“Yes…”
She smiled like she expected that answer, then motioned toward the big guy’s notebook with her chin.
“Is what he wrote correct?”
A ss of formulas, faulty derivations.
Does he not see the orbital path from his equations? If it moves like that, the planets would eventually crash into each other.
“No. You don’t need orbital chanics for that problem. Basic astronomy, Newtonian chanics, and Kepler’s laws are enough to derive the answer.”
At my words, the big guy’s face turned red.
"Can you take responsibility for those words?"
There was a hint of threat in his voice.
I sighed. This is exactly why I didn’t want to get involved...
But once I’d started talking, I couldn’t back down. Plus, his attitude was a bit off.
“Yes, I’ll show you.”
I pulled out my notebook and duck pencil from my bag.
“First, according to Kepler’s First Law, the orbit of a planet is an ellipse with the Sun at one focus.”
Scratch, scratch.
“And using Newton’s law of universal gravitation and centripetal force…”
[F = GMm/r² = mv²/r]
“From here, if we find the angular velocity and apply Kepler’s Third Law, we can derive the relationship between the semi-major axis of the orbit and the orbital period.”
I carefully developed the formulas step by step.
Suddenly, the surroundings went quiet. Everyone was watching my fingertips.
“Therefore, if we substitute the conditions given in the problem…”
When I finished the calculations, the exact answer ca out.
“Like this.”
A mont of silence when I put down the pen and looked up.
The big guy was staring at my answer, mouth wide open.
The students next to him looked at with suspicion.
“Is this really correct?”
Do they not understand it even after seeing the solution?
“Try substituting and verifying it.”
The group hurriedly pulled out their calculators from their bags.
Tick, tick, tick.
Then, a mont later, the sa number that I had written in my notebook appeared on their calculators.
“It’s real…”
An awkward silence hung in the air.
“This is hilarious! Who’s teaching who now?”
A high-pitched voice ca, sounding oddly amused.
Noona picked up her tray and stood up. Then she signaled with her eyes to follow.
“Since the two IMO spots are for and him, the rest of you can figure it out yourselves.”
She pulled away from the table and led out.
Ah! I haven’t even finished the lunch Mom packed for yet.
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