90608
In this sentence

> ミサイルは高【たか】さ100kmより低【ひく】い所【ところ】を東【ひがし】に750km飛【と】びました  
>  _The missile flew 750 kilometers east at a height lower than 100
> kilometers._

appearing here
<https://www3.nhk.or.jp/news/easy/k10013261541000/k10013261541000.html> the
recording sounds like there is gemination between the end of ひゃく and the
beginning of キロメートル.

What is the orthographically correct way of writing "100km"?

> ひゃっキロメートル

or possibly

> ひゃッキロメートル
CC BY-SA 4.0
2021-10-03T07:19:08.717
90606
2021-10-15T19:23:55.623
2021-10-03T21:01:06.330
1628
31150
question
orthography numbers gemination
gemination orthography
I agree with @Simon in the comments: since the gemination comes from the く in
ひゃく, ひゃっ should be the natural choice when writing ひゃっキロ in kana and I would
not be too surprised to see

> [100]{ひゃっ} [km]{キロメートル}

as _furigana_ in a textbook. (That said, in all textbooks for beginners I
could find, there actually seem to be no _furigana_ at all — try to search the
web for images with something like `単位 教科書`.)

Note that numbers are usually not written in _kana_ , so one should not expect
any reliable corpus data to confirm this — e.g. the Balanced Corpus of
Contemporary Written Japanese has 0 hits for both ひゃっキロ and ひゃッキロ.

However, @a20 has found a paper titled "Morphology of numerical expressions in
contemporary Japanese", where the pronunciation of numbers plus counters in
written in kana and you can find the following:

> [![enter image description
> here](https://i.stack.imgur.com/DY5f8.png)](https://i.stack.imgur.com/DY5f8.png)

Also interesting is the following:

> [![enter image description
> here](https://i.stack.imgur.com/qXrIl.png)](https://i.stack.imgur.com/qXrIl.png)

which says that for 6 and 100 (which end in く), gemination essentially always
occurs, but for 1 and 8 (which end in ち), there is some variation.
CC BY-SA 4.0
2021-10-03T20:59:03.737
90608
2021-10-15T19:23:55.623
2021-10-15T19:23:55.623
1628
1628
90606
answer
In response to the comment above...

_since the gemination comes from the く in ひゃく, ひゃっ is more sensible than ひゃッ_

I can add the following sentence found here

<https://www.asahi.com/articles/ASN7F2QDMN76UPQJ009.html?iref=pc_extlink>

長期休【ちょうきやす】みが来【く】るとホッとしたし、終【お】わりに近【ちか】づくと「また学校【がっこう】が始【はじ】まる」とつらかった

_I was relieved when the long vacation came, and when it was nearing the end,
it was hard to think that school would start again._

in which we see the following vocabulary item with two different gemination
orthographies, according to Jim Breen's wwwjdic:

ホッとした from : ほっと(P); ホッと(P); ホっと (adv,vs) (1) (on-mim) with a feeling of
relief; with a sigh of relief; (adv) (2) (on-mim) deeply (sigh)

In light of this example, it consequently appears hard to justify the
statement that "gemination comes from" a word, or that any particular
orthography is "more sensible." Perhaps responses should be based on
objectifiable information, such as frequency of a word's or a spelling's
occurrence or at least percentages of their acceptability as determined by
polls.
CC BY-SA 4.0
2021-10-10T07:12:06.323
90684
2021-10-10T16:17:29.280
2021-10-10T16:17:29.280
31150
31150
90606
answer