"Maths in Japanese" (Math and CS book club)

Looks like the first week is almost over already. How is everyone doing? Some of you were busy preparing (and taking) the JLPT and some of you are in the middle of some exam period, right? Hope, everything works out well :slight_smile:

This week we had four videos in total so it is a lot of different material to cover. We will have less videos in the upcoming weeks.

In general, I think the videos are very convenient to follow along. So for those of you who are more into extensive than intensive reading or listening this series seems to work pretty well, I think.

Personally, I’m very happy I came across the terms 「Oのくらい」and「つなぐ」which I learned with our previous book club :star_struck:

Next week we will read our first Wikipedia article. I’ll post a proposal for those of us who do not wish to read the full article later / tomorrow depending on your timezone. I think I’ll stick with the ones I made in our home thread but I’d like to properly link them to some of the material we covered during this week.

Last but not least I am thinking about making some short quizzes so you have something more to Poll on. So stay tuned :blush:


I just watched the videos and they’re really well done and to the point, I enjoyed them.
I thought the notation for repeating decimals with a dot on top was interesting, I’ve never seen that. Is it just a Japan thing? Pretty sure they never taught me this in school.

I didn’t really want to commit to this book club so I haven’t been participating in the polls, just stalking, but we’ll see how things go :slight_smile:


Oh, please! I love quizzes.


I live in Canada and I’m pretty sure I was taught this in school so I don’t think it’s just a Japanese thing.


Welcome to week two. Let’s see who will read along this week :slight_smile:

Week 2 ~ Are you reading with us?
  • I’m reading along
  • I’ll catch up later
  • I’ll skip this one
  • I’ve dropped it completely
  • Nope, only here for polling :upside_down:

0 voters

This week we will read about “Natural Numbers”. Everyone who wants to read the full article feel free to do so.

Everyone who only wants to read part of the article feel free to chose something from the following parts:

  • [1] Introduction: here you’ll get a brief introduction to what a natural number is. It relates especially to the video Math 1.4 as it embeds the natural numbers into whole numbers / integers and addresses the “problem” with the number zero.

  • [2] 記法: here you’ll learn different mathematical notations for what is addressed in [1]

  • [3] 特殊な自然数: here you’ll the terms for prime numbers will be revised. Again, this one relates to Math 1.4, I think.

  • [4] 形式的な定義: here you’ll get a mathematical definition on what a natural number is. Some vocabulary terms from Math 1.1 are used and you can practice reading equations. ( → E.g. do you remember the terms for “brackets” :wink: ) You’ll also learn the terms for distribution law or commutative law and others. Some of them we will see again in week eight when we read about vector spaces.

My recommendations:

  • [1] and [2] go very well together. Especially in case you are busy with other book clubs or RL stuff. You can extend it to [1], [2] and [3].

  • [4] Seems to be very nice in case you want to enhance the topics discussed in week 1.

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Thanks for sharing. There might be different ways to mark repeating decimals. Sometimes you can see a straight line on top of them instead of the dots :slight_smile:

Absolutely feel welcome to go on your own pace. I think, this book clubs works very well to hop on and off on a weekly basis.

…and here is what I came up with so far :blush:

1.「 7*6=42 」は何と読みますか。

  • ななろくよんじゅうに
  • ななろくが よんじゅうに
  • なな タイム ろくは よんじゅうに
  • なな かける ろくは よんじゅうに

0 voters

2.「 \frac{8x - 4y}{12} 」は何と読みますか。

  • Please see the following post for correct answers. の is missing after ぶん.
  • はちエクス マイナス よんワイ ぶん じゅうに
  • じゅうに ぶん はちエクス マイナス よんワイ
  • はちエクス ひく よんワイ ぶん じゅうに
  • じゅうに ぶん はちエクス ひく よんワイ

0 voters

3.「 10/3=3 \cdots3 」は何と読みますか。

  • じゅう ぶん さんは さん あまり さん
  • じゅう ぶん さんは さん てんてんてん さん
  • じゅう わる さんは さん あまり さん
  • じゅう わる さんは さん てんてんてん さん

0 voters

  1. 1.8+8.2=10 」は何と読みますか。
  • いちてんはち たす はちてんには じゅう
  • いってんはち たす はってんには じゅう
  • いってんはち プラス はってんには じゅう
  • いってんはち プラス はってんにが じゅう

0 voters

  1. 少数にはなんのものがありますか。
  • 有限少数
  • 無限少数
  • 循環小数
  • 非循環小数

0 voters

  1. 分数の種類を選んでください。
  • 正の整数
  • 負の整数
  • 真分数
  • 仮分数
  • 帯分数

0 voters

  1. 素数を選んでください。
  • 1
  • 2
  • 3
  • 4

0 voters

In the first couple of questions I added some spaces. It’s still messy but I hope with the spaces you have some chance to read along.

I’m usually very good in making mistakes … please don’t be shy and point the out :sweat_smile:

Feel free to discuss the quiz in here but maybe use spoiler tags or

Spoiler alert

hide tags

so others will be warned.


I think that question 2 is missing の after ぶん. Nice quiz otherwise!


Not gonna lie, those videos were pretty challenging and fast for me (probably because I still need to work on my listening skills), but hopefully as we go along I’ll get used to them more (or maybe just put them on 0.75x speed lol).


He definitely speaks fast. No shame in slowing it down.

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Ooh those quizzes are really cool, thanks for creating them! I probably won’t be able to start reading along for another two weeks but I’m really looking forward to finally being able to read equations in Japanese instead of just switching to English :sweat_smile:

1 Like

One notation that is also used is having a bar on top of the repeated decimal.

I’m planning to catch up later with this thread when I’m back home properly.

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Well spotted. Thanks for sharing, I appreciate it.

Absolutely agree. I hit the pause button more than once to actually “read along”.

The speed itself might be considered normal speed but the content is quite dense, I think. So there is a lot of terms to process within seconds. I’m still amazed how much vocab he manages to fit into those few minutes :slight_smile:


So here comes the advanced version :innocent:

7.2 素数を選んでください。

  • 294001
  • 394001
  • 293001
  • 294002

0 voters

I’m wondering if @RoseWagsBlue senpai would be interested in this one as well :thinking:


I think the speed is fairly quick. If I compare it to my workplace, usually people only speak that fast in meetings or on the phone. Otherwise, people speak much slower unless they’re injecting in conversation.

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I’ve only watched the first two video so far, but I’m pleasantly surprised by how much I already knew from WK and my Japanese friends. I had to repeat a couple of sections, but it was otherwise good. I think I’ll probably rewatch them later anyway though to check my retention.


The advanced quiz was very fun: the last two were really easy to eliminate, and luckily I didn’t have to try too many 素数 ending in 1, 3 or 7 before finding that the second one is divisible by by 47.

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I liked the videos very much. There were a couple of sections I didn’t bother to understand in detail. The section on コンマ I only got the gist of. I think it says the comma is only used for microseconds, and you can leave off the 0 before the 点。 He talked for a while, though, so I’m pretty sure I missed something.


Thanks for sharing your thoughts on the first couple of “Math in Japanese” videos.

You may have seen it already but I want to mention the recent discussion on basic arithmetic terms in Japanese. There is some more resources linked to make out the nuances on terms like 加法 and 加算 and others. Feel free to check it out.

And for those who are interested I’ll leave some links on the

Mathematical background on week ones' Q7.2

The question is taken from an example on some research on so called “digitally delicate prime numbers”. The paper is published on arxiv:

Quanta magazine also wrote an article about it:

EDIT: and here is a link to a YouTube video going through the paper shared in the home thread:


Yeah,I did not really catch that one either. At least at some point I went over it instead of really looking into the structure :see_no_evil: But if you come across sentences or topics you’d like to make sure about always feel free to ask about it in here.

Glad to read that :slight_smile:


So far I’ve collected over 100 math words to study in the near future (though I’ve memorized probably half of them already just from reading a bunch of Japanese math Wikipedia pages the last handful of days!). So far I’ve mostly focused on arithmetic and geometry. I do plan to watch the rest of these YouTube videos to learn some more and gather more words too.


Welcome to week three :slight_smile:

I’m super curious how the first WP article of this book club went for you. Who did read the full article? Who did read parts of did? What did you learn from it? What maybe surprised you?

Let’s start with the weekly participation poll though:

Week 3 ~ Are you reading with us?
  • I’m reading along
  • I’ll catch up later
  • I’ll skip this one
  • I’ve dropped it completely
  • Nope, only here for polling :upside_down:

0 voters

How did the reading about Natural Numbers go?

  • I’ve read the full article and pace works fine for me
  • I’ve read the full article but will only read parts for the upcoming WP articles
  • I’ve read parts of the article and pace works fine for me
  • I’ve read parts of the article but will aim for the full one next time
  • I’ve read parts of the article but will aim for little bit less next time
  • Just here for polling :upside_down:

0 voters

Apart from that I managed to durtle around in the forums for the last 2~3 hours :see_no_evil: So quizzes will probably have to wait until later / tomorrow. But feel free to share your thoughts and questions.