The little kid had a big round face and tiny eyes, like two black beans dotted on a white steamed bun. Right now, he was glaring at her, cheeks puffed out, as if she’d never hear the end of it if she dared cross the invisible line between their desks—a look that was especially adorable.

David Carter reached out and pinched the kid’s cheek. There was a bruise there—she’d given it to him yesterday.

That’s right, the student from Class 10, Grade 5 of Red Star Primary School who was chosen along with her for the Olympiad math class was called Brian Foster, the homeroom teacher’s son, and little David Carter’s number one nemesis.

She smiled, greeting him magnanimously, “Brian Foster, you’re here.”

Little Brian Foster shuddered and slapped her hand away. “Are you crazy?!”

“Crazy or not, it’s not illegal for me to hit you.” David Carter whispered, then turned her head to flip through her book.

“Crazy orphan!” Brian Foster exploded, shouting at her.

The classroom fell abruptly silent.

“Brian Foster!” At the podium, the female teacher who had just entered was so angry her face turned pale.

David Carter also jerked her head up. She’d only meant to tease Brian Foster, not expecting that his own mother would walk in at that very moment.

Brian Foster’s mother, Mr. Thompson, slammed down her textbook and a stack of graded workbooks she was carrying, and strode over to their desk in high heels.

David Carter figured that if they were at home, little Foster’s butt would already be sore. But since they were in class, Mr. Thompson had to save her son’s dignity.

“Apologize to David Carter.” Mr. Thompson’s expression was cold and stern, extremely serious.

Brian Foster was startled by his mother, his eyes turning red with fear. Reluctantly, he turned his head and started to sob, “S-sorry…”

“The background of other students is not a reason for you to attack them.” Mr. Thompson added, as if speaking to the whole class.

David Carter pressed her lips together. Honestly, what Brian Foster had said earlier had stung a little.

But now, not at all.

……

This lesson was the second part of “Boats Traveling in Currents.” The core of all such problems was two formulas.

Downstream speed = boat speed + current speed

Upstream speed = boat speed – current speed

Mr. Thompson was explaining these at the podium. David Carter had learned them once ten years ago. Back then, she’d thought the lesson was quite tricky—the interplay of downstream, upstream, boat speed, and current speed was especially confusing. But now, relearning it, everything seemed crystal clear. It wasn’t that her intelligence had improved dramatically since fifth grade, but her ability to understand problems had changed.

V_boat = (V_downstream + V_upstream) / 2

V_current = (V_downstream – V_upstream) / 2

Looking at the content on the blackboard, David Carter started copying it down.

“V_boat = …”

She hadn’t even finished half the formula when the smooth, mature handwriting on the thin paper startled her. If a fifth-grade girl wrote like this, she must be a true disciple of Pang Zhonghua. She quickly switched to her left hand and copied down all the formulas the teacher wrote on the blackboard.

Little Brian Foster was right-handed, and his right elbow kept bumping into her left hand, so every couple of characters they’d collide, making it uncomfortable for both of them to write.

But maybe because his mom had scolded him in front of the class, little Foster looked annoyed but held back his temper. When he made a mistake from being bumped, he just furiously erased the paper with his eraser.

David Carter had no choice but to shrink into the corner and do her best to write.

Finally, it seemed little Foster couldn’t stand being bumped every two characters anymore. He slammed his pen down, his little black-bean eyes glaring fiercely, looking just as fierce as his mom when she slammed her book.

“Why’d you suddenly switch hands? So troublesome!”

Because my handwriting is too good and I’m afraid you’ll get suspicious.

David Carter thought silently.

But before she could come up with an excuse, she heard Brian Foster declare with bossy confidence, “Next class, we’re switching seats. I’m sitting on the inside!”

David Carter couldn’t refuse, and could only look at little Foster’s white-bun face, barely resisting the urge to pinch his cheek again.

But this time, they didn’t get the chance to switch seats during the Olympiad math class.

During the break, as soon as Mr. Thompson put down the chalk, she said, “Class, use the ten-minute break and the first five minutes of the next period for a pop quiz.”

The rest of the class groaned. David Carter spun her pen—she hadn’t taken a test in a long time, but she actually felt excited.

The test papers were handed out quickly, a thin and brittle A4 sheet. Mr. Thompson was well prepared and had printed them in advance.

There were ten word problems in total, but only fifteen minutes to finish. That meant only a minute and a half per question—a real test of speed and accuracy.

David Carter skimmed through all the questions.

Ten word problems.

Three on the “principle of inclusion and exclusion.”

Three on “cows eating grass.”

Three on “boats traveling in currents.”

And the last one was a bonus question related to boats in currents—technically just taught, but not really, as it was a sixth-grade level problem.

The only sound in the classroom was the rustling of pens on paper. David Carter paused for a moment, realizing she was facing a bit of a dilemma.

Not because she couldn’t do the problems, but because she could do them too well.