Regional Olympiad Challenge (2)
“Ha, ha, I guess I solved it pretty fast once I got into it…. Hehe~”
“……”
The seniors gaped at her like she was an alien, along with Mr. Oh Se-jun. Jeong Hae-won, at least, kept a relatively unimpressed expression, having witnessed my skills multiple times before.
“For real? You solved all five problems in under three minutes?”
“I’d need at least ten minutes for that one myself.”
“Hey! Solving a problem this tough in ten minutes would disqualify you from the competition!”
“……”
As the other seniors erupted in chatter, only the sister with her hair pulled back tightly in a ponytail showed a flash of frustration. She bit her lip hard and gripped her pencil like she was about to snap it.
What’s her deal? Did I earn her grudge by solving it too fast?
Soon, Mr. Oh Se-jun calmed the heated classroom. Class wasn’t over yet, after all.
“Everyone, get your heads straight. You might not match Seoyeon, but you need to finish in under five minutes max. No more than a minute per problem! Got it?”
“Yes!”
After that, Mr. Oh Se-jun handed out more test problems several times. Around the thirty-ninth one, maybe? I scrutinized the next problem carefully. Finally, I reached the last one.
(40) The sides of a triangle are x, x+2, and x+4. Find the value of x that maximizes the area of the triangle.
It looked similar to problem five from before at first glance. But the difficulty was worlds apart. To solve it, I might need to bust out Heron’s formula from high school math.
This is straight-up high school level….
As expected, this regional academic competition seemed to include a few killer problems designed to prevent perfect scores and boast insane difficulty.
I set the sides as a, b, c respectively and calculated the semi-perimeter s. Scratch-scratch!
As I worked diligently, Mr. Oh Se-jun stood beside me. He frowned deeply, silently watching my solution process.
Like someone possessed, I kept my pencil flying nonstop. Fortunately, I nailed the semi-perimeter s in under twenty seconds. Then plug that into the formula and calculate each term to get the area.
For a fixed perimeter, a triangle’s area is maximized when the sides are as equal as possible, approaching an equilateral triangle. That’s the peak.
The given sides were x, x+2, x+4, with x+2 in the middle. To make them as equal as possible, that middle value should be the baseline. The most natural way is when the sides are nearly identical, and calculating from there gives the maximum area.
Got it!
I plugged the values back into the condition to verify and wrapped it up.
“Perfect.”
“Huh?”
Mr. Oh Se-jun, who never handed out even a speck of praise, slowly nodded and tapped his finger on my solution.
“The last one mixes in some high school material, but you solved it flawlessly. Where’d you learn this?”
“No, I just… figured it out as I went….”
“Really? A first-grader just ‘figured out’ how to use the tricky Heron’s formula from high school curriculum without a hitch?”
It was a fair point that didn’t make immediate sense. That’s where being born into the Hansung family came in handy.
“I see. Chaebol kids get elite tutoring from a young age, so learning high school stuff at your age isn’t so surprising.”
Nod nod! I bobbed my head up and down vigorously. If he was kind enough to misunderstand on his own, it sure made things easier for me.
An hour passed. Mr. Oh Se-jun went to the front and clapped three times with his palm.
“That’s it for today! Whatever you couldn’t solve, study it at home and come back tomorrow. Seoyeon, after supplementary class, swing by the office and grab more problems from me! Class dismissed!”
“Thank you!”
After class, one figure scampered over. None other than Jeong Hae-won from the Hyun-do family.
“Seoyeon, how’d you solve this? Number 32—they gave it to us to solve, right?”
“Oh, that one.”
The other seniors, who’d been eyeing me warily at first, gradually gathered around my desk.
“Um, haa…. It’s kinda weird for a senior to ask a junior, but with our situation, we don’t have time to beat around the bush. Straight up—wanna study together outside of supplementary class? Just us?”
“Huh? Study?”
“Yeah. It’s shameless, I know, but bombing the regional competition would be total humiliation. You know our school’s reputation and position.”
Ah! She was proposing a study group. The one speaking for them was Gwang-woo, the sixth-grader. He’d gotten thoroughly thrashed by the genius girl from Samcheong-dong last time, so his resolve burned extra hot.
“Sure. Let’s all work hard together.”
“Thanks. I’ll repay this favor later. Everyone hear that? We have to get good scores. Or else….”
Or else face Mr. Oh Se-jun’s infamous two-hour special counseling session—the devil of the school.
“Eek!”
The seniors paled as if reliving a nightmare.
＊
A week passed. After regular classes at school, I headed to the supplementary classroom as usual without fail. Once that ended, the competition participants gathered separately for problem-solving and review. Thanks to that, Hae-won and the seniors improved by leaps and bounds day by day.
“Seoyeo-o-on, wait u-up!”
Jeong Hae-won toddled after me like a baby duckling. As always, her mouth ran nonstop today too.
“That number 24 from yesterday’s class—I agonized over it all night but couldn’t crack it. How’d you do it?”
“Oh, that? Well….”
I recalled it and answered softly.
“The key is spotting the sequence pattern first. Brute-forcing calculations just drags on forever. Compute the first few terms manually, and you’ll see the common difference isn’t constant—there’s a hidden relation between terms. So instead of jumping to the general term….”
We’d arrived at the supplementary room. Gwang-woo oppa and a few seniors were already there, noses buried in workbooks.
“Hi?”
“Oh? Seoyeon and Hae-won are here?”
The seniors stood and clustered around me. A week into supplementary class, the scene before every session was always the same. They all bombarded me with their unsolved problems.
“This one? Straight calculation hits a trap. Don’t chase the numbers—look at the expression’s shape first. Compare front and back terms, and the pattern repeats. Grab that flow, and it sorts out without messy math.”
“Ooooh!”
This time, another senior pointed to a different problem.
“This… you’ll need to set up a telescoping series, right?”
“Telescoping? What’s that?”
I picked up my pencil and explained where they could see.
“See this formula? Break it down small, expand the terms, and front and back cancel out sequentially. The messy sum cleans up to just the first few terms.”
“Whoa, the solution really simplifies!”
“Yeah. I used telescoping for this one too.”
“Ooooh!”
Mr. Oh Se-jun entered midway through my explanation. Everyone hurried back to their seats.
“Hm? One seat’s empty. Who’s missing?”
Now that he mentioned it, one spot was vacant. Who?
“Uh… that’s Mi-yeon. She hasn’t shown up yet.”
“Mi-yeon? Why?”
Kim Mi-yeon—the ponytail girl who’d provoked us on the first day of supplementary. Guess she hadn’t come to school today.
“I see. Missing even one day throws you way behind…. What to do?”
Call it what it was, but Yeonhwa Elementary was a special school packed with Korea’s top students. Naturally, Gwang-woo oppa’s family was big in legal circles, the other seniors from prestigious houses, and the girl sniffling and solving problems next to me was Hyun-do Group’s granddaughter, Jeong Hae-won.
But Kim Mi-yeon was different. Pure merit got her in—no family backing, just hard work. Sure, her background was a step below the others, but still upper-class. It just felt ordinary at Yeonhwa.
“Seoyeon?”
“Yes?”
Mr. Oh Se-jun called on me as I pondered.
“You’re ahead of the others, so I’ll let you finish ten minutes early. Take this formula card and solutions I wrote to Mi-yeon.”
“Okay!”
Her house was on the way to Bukchang-dong anyway, so stopping by wouldn’t hurt.
Kim Mi-yeon’s home was in the next neighborhood over from Bukchang-dong. A short detour off the bustling street led to a quiet residential area, her house tucked deep inside. After seeing only grand mansions like the Hansung or Hyun-do chairman’s, it’d been ages since I’d seen such a modest place.
Ding-dong!
I rang the doorbell. A faint rustle came from inside.
“Who is it?”
“Um… I’m Han Seoyeon. Since Mi-yeon unnie didn’t come to school today, I’ve got something to deliver for her.”
“Who? Han Seoyeon? That Han Seoyeon?”
Huh? The voice from beyond the door felt oddly familiar. The door cracked open, revealing Kim Mi-yeon peeking out—hair tied back tight with a rubber band, as usual.
“…What brings you here?”
“Oh, uh… Mr. Oh Se-jun asked me to pass this along. Missing even one supplementary day makes it super hard to catch up.”
“Oh? Th-thanks….”
We weren’t close, so I figured I’d drop it off and head back to Bukchang-dong. But—
Grab!
“!”
Suddenly, a hand clutched my collar. I turned—Kim Mi-yeon gripping it tight.
“You okay?”
She had a cold damp cloth on her forehead and neck. Looked like the flu. Ah, that explained skipping school.
Honestly, even as a higher grader, she was just an elementary kid. Yeonhwa’s curriculum was notoriously grueling. Regular classes were one thing, but piling on supplementary and study group? Her body couldn’t take it.
“Um, hey….”
Kim Mi-yeon fidgeted with her fingers and mumbled softly.
“C-Could you… stay at our house a bit before you go?”