What are the rules for reading numbers before a foreign counter-word?

Question

Is there a rule of thumb for knowing the reading of a number when it is written in western numerals, and is followed by a loaned counter-word?

For example, how would you pronounce the "1" in １セット? My first thought it to say 「いっセット」, but as far as I know it could just as easily be 「ひとセット」 or 「いちセット」. The Wikipedia article does not cover loan-word counters, and I cannot find anything on this topic.

Answer 1

I'm going to extrapolate the rules for Japanese counters onto foreign-counter-words.

Extracted from Nihongoresources:

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Rules for 一

• When followed by a counter starting with a syllable from the か—, さ— or た—column, いち becomes いっ

• When followed by a counter starting with a は—column syllable, いち becomes いっ and the counter changes to a 'p' sound

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Rules for 三:

• When followed by a counter starting with a は—column syllable, that syllable changes to a 'b' sound

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Rules for 六:

• When followed by a counter starting with a か—column syllable, ろく becomes ろっ

• When followed by a counter starting with a は—column syllable, ろく becomes ろっ and the counter changes to a 'p' sound

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Rules for 八:

• When followed by a counter starting with a か—, さ— or た—column syllable, はち becomes はっ

• When followed by a counter starting with a は—column syllable, はち becomes はっ and the counter changes to a 'p' sound

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Rules for 十:

• When followed by a counter starting with a か—, さ— or た—column syllable, じゅう may become じっ or じゅっ

• When followed by a counter starting with a は—column syllable, じゅう can become either じっ or じゅっ and the counter changes to a 'p' sound

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In short I don't think it matters if the counter is of Japanese origin or foreign origin. It depends on the first syllable of the counter.

Answer 2

Following this advice on Meta, I'm going to throw in an answer I'm pretty sure of, but could be corrected on.

Scanning down the list of example counters in the Wikipedia article you linked to, every one of them starts with 一{いち}, or it's phonetically adjusted equivalents like 一{いっ}. There were a lot, though, so maybe I missed one or two exceptions.

Thus, the rule of thumb I think you're looking for is:

Unless you already know for sure it's an exception, always guess the counter starts with 一{いち}/一{いっ}

I think this could be said for just about all counters, not just foreign words. Since you're asking specifically about "loan-counters," though, the point is that this rule of thumb would encompass them as well.

I can't think of an example exception, along the lines of 一人{ひとり} and 二人{ふたり}, that uses a loan-word in the counter.