it's ひゃく　hyaku, not ひやく　hiyaku びゃく　byaku ぴゃく　pyaku 100: Hyaku. 200: Nihyaku. 300: Sanbyaku. 400: Yonhyaku. 500: Gohyaku. 600: Roppyaku. 700: Nanahyaku. 800: Happyaku. 900: Kyuuhyaku.

That B/P/P technique was really helpful...thank you so much. Now I can remember all of them. ありがとうございます。。。がんばります! ^_^

Arucard303 is absolutely correct. Kanji-wise, it's the same character, but remember 3, 6 and 8 are your changers. B comes before P and 3 is the smallest digit of the changers, so 3/6/8 = B/P/P. Although, if you look: さんびゃく「三百」、ろっぴゃく「六百」、はっぴゃく「八百」。Notice the Kanji doesn't change, just the pronunciation. がんばって！