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Different pronunciations of 人 in one sentence?

「何百人もの人がそこにいた。nan byaku nin mono hito ga soko ni ita」＝There were hundreds of people here.
When you count the people, you have to use this character「人」pronounce is "nin", so 「十人」ju-nin「百人」hyaku-nin 「千人」sen-nin　etc.
(But, this case 「百人」with 「何」, so becomes "nan-byaku-nin", not "nan-hyaku-nin".)
The pronouciation is ---
First 「人」--- "nin"（numeral classifier）, second 「人」--- "hito"(noun).
(「人」is pronounced also "jin"　ex「日本人」nihon-jin)
In this case 「何」is like "some".　
When you don't know how many people but you know more and less, use this character with numeral or numeral classifier directly (「何人nan-nin」).
「何百人」＝hundreds, 「何十人nan-ju-nin」tens, 「何千人nan-zen-nin」thousands

I hope that you understand my bad english.