Clarification with numbers

[Amylg05]

Hi all,

I have just started working through the Genki I workbook and there's an exercise on the cost of items. This might be a silly question but if I want to write 100 or 1000 are this simply ひゃく and せん or do I need to put いち before them to show that it's "1 hundred" and not just "hundred"? In the workbook it doesn't show 100 and 1000 with いち before them but for 10,000 it is いちまん so I got a little confused and don't want to continue the exercise without knowing what's correct! Thank you ^_^

 

[Shutainzu]

You don't need いち in front of ひゃくor せん. So for example if you were trying to say 100 yen it would be ひゃくえん and for a 1000 yen せんえん。

 

[Toritoribe]

In addition, it's a bit confusing, but 1 million is also ひゃくまん without いち, but 10 million is いっせんまん, not just せんまん. Furthermore, as for 10 million~20 million, "ichi" is optional, thus, 12 million is せんにひゃくまん or いっせんにひゃくまん. The same goes to 100 billion~200 billion or more.
100: ひゃく
1000: せん
1200: せんにひゃく
10 million: いっせんまん
15 million: せんごひゃくまん or いっせんごひゃくまん
100 billion: いっせんおく
170 billion: せんななひゃくおく or いっせんななひゃくおく
Japanese numerals - Wikipedia

As you can see above, the point you need to pay attention is 10 million, 100 billion and so on. いち(いっ) usually can't be omitted in these ones. Other cases such like 15 million or 170 billion, there is no problem with just せん without いち(いっ).

 

[Majestic]

This might be a silly question

Not at all a silly question. I still struggle with this myself.

 

[Amylg05]

Thanks everyone