The maid squad is too strong, what use is there for me, the Demon King?

After reading the question, a huge "That's it?" flashed through Gray's mind.

This is a primary school level question, right? But Lia is only 14 years old, and she can only answer questions of this level, which shows that the math level in this world is really not that great.

Or is it that Lia's studies are not deep enough?

"It's adding numbers from one to one hundred, not just those six numbers!" Leah even spoke up to correct Grey, preventing him from misunderstanding the problem: "Is this problem really that awful? She herself wouldn't even write out the complete problem, and now I have to calculate it..."

"Calculating all this is exhausting."

Lia had already written down the answer, and when Gray saw the number 4, he already understood the problem.

Liya went straight to 100 from the beginning, which was obviously troublesome. She even got it wrong, and the result was quite different from the correct answer. She probably made a mistake or missed a lot during the calculation.

Gray asked tentatively, "Didn't your teacher, Erika, teach you how to answer questions like this?"

Lia shook her head: "Some of the questions she assigned weren't taught, but this one doesn't count, right? It should be testing patience and attention to detail..."

Gray roughly understood what Ms. Erika was trying to say.

Developing critical thinking skills is crucial; anyone who actually tries to add one to one hundred is a fool. It seems my younger sister isn't very bright in this area, though, when it comes to math.

This might be a little cruel to Leah, who has patiently finished calculating, but Gray still has to say it: "You've got it wrong, 5050, you're still quite a distance from the answer..."

"Huh?" Lia was taken aback.

"Huh????????????????"

Gray's answer seemed more reasonable.

Leah looked up with some suspicion: "Brother, really? You're not just making up a number to trick me into calculating it again, are you?"

Gray looked slightly exasperated: "Do I look like I have nothing better to do?"

“Actually, you’re quite idle at home, aren’t you…” Lia tilted her head slightly and muttered in a very low voice.

"Huh?" Gray stared.

"It's nothing..." Leah quickly admitted defeat, then pouted again:

"Then how did you know the answer? You only saw the question a short while ago; it's impossible to calculate it in such a short time..."

Upon hearing this, Gray laughed and said, "There are techniques involved; it's not something you can figure out by rote."

The nine years of compulsory education I received in my previous life, which I taught Aiota, have come in handy again!

Liya looked unconvinced, and Dadi didn't believe his older brother knew these things: "Then tell me, what are the techniques?"

Grey decided to show Leah a bit of the shock of nine years of compulsory education.

"Simple, sum of arithmetic sequence, multiply the first term by the last term, divide by the number of terms, 5050, done in seconds."

"……………………………………" (?°?°?)? Lia looked bewildered: "Huh?"

"Brother, are you kidding me?" (｀へ′*)ノ Liya puffed out her cheeks.

If you just throw a formula at her right away, Lydia definitely won't understand. Of course, Gray didn't intend to teach her that way.

Elementary school problems should be solved using elementary school solutions.

"No, I'll teach you a method you can understand," Gray said with a smile.

Lia gently clenched her fist...

This sense of superiority and unconscious intellectual superiority is infuriating.

"All ears."

Lia vowed that if her brother couldn't come up with anything worthwhile today, she would definitely give him a good sarcastic rebuke.

Teaching begins.

"Let's not look at this question yet. Let me ask you first, what is 1 + 99?" Gray entered teaching mode.

I feel a bit nostalgic, after all, that's how I used to teach Aieta, and now Aieta has long since graduated and can still come up with quite a few new things.

“100,” Lia replied immediately. “I can solve it quickly even if it only involves two numbers.”

“Very good.” Gray nodded. “Next, what is 2 + 98?”

莉雅无奈道：“也是100，3+97、4+96、5+95也都是……欸？”

Lia seemed to realize something, and her tone faltered.

Grey could tell from Leah's expression that she must have figured it out; it seems this little girl has some understanding.

“一直到49+51也都是100，把这样的两个数放在一组，一共49组，剩下的50、100额外计算。

1+2+3+……+98+99+100=49x100+50+100=5050。”

Lia fell into deep thought.

Then he suddenly realized what was happening and gasped.

"Brother, you're a genius!" Σ(°△°|||)︴? Lia's face was filled with shock.

“Uh…” Gray couldn’t possibly agree. If this level of talent was considered genius, then wouldn’t geniuses be everywhere on Earth in his previous life?

Liya was so excited that she couldn't help but rush over and say, "Brother, you're so good at math! Teach me!"

Gray silently blocked Leah's physical contact and said, "I can teach you during the break, and this is the only thing I can teach you..."

Leah seemed very happy, finally getting hands-on instruction from her brother... oh, wait...

Finally, someone can teach her math!

"Then let's not delay!"

Lia pointed to the next question: "I couldn't solve this one, can you take a look, brother?"

What about Lia? She didn't write it out.

Gray wanted to see what kind of "baby bus" it was, so he looked over.

This is still a big question, and you'll need to read some text.

"Given a certain number of rabbits and pheasants, these rabbits and pheasants are placed in a cage. The total number of heads is sixty, and the total number of feet is two hundred. How many rabbits and pheasants are there?"

Gray: "..."

Both the Feathered Rabbit and the Wool Chicken are a type of unranked (or zero-rank) magical beast. They are herbivores and pose no real danger. However, due to their delicious meat, they are widely raised by humans as a source of food.

Feathered rabbits and harpy chickens have more feathers than normal rabbits and chickens, but there is no difference in other aspects.

The rabbit still has four legs, and the pheasant still has two legs.

Isn't this just a classic case of the chicken and rabbit being trapped in the same cage?

I never expected to encounter the "chicken and rabbit in the same cage" problem in another world, especially one with an isekai (another world) theme.

That second-grader, yes, no higher, solve this problem and give Leah a little shock...

Unfortunately, that won't work; Gray doesn't have any second-grade elementary school students.

Do the mental calculation.

x + y = 60

2x + 4y = 200

Equation 1 x Equation 2 is set as Equation 3

Type 3 - Type 2

……

Lia's eyes were full of anticipation; she was really stumped by this question.

Who would be so kind as to put a feathered rabbit and a woolly rabbit in the same cage?

Can your brother make it? How long will it take him to make it?

"The solution is x=20, y=40".

Lia: "Hmm... Hmm?"

What is this all about? Where did x and y come from? And what are x and y?

Grey knew that Leah must be confused again, so he said, "It's 20 velvet chickens and 40 feathered rabbits. You can check it yourself and see if it's 60 heads and 200 legs."