Learning Japanese - Lesson 2 - Counting Number 1 - 100

1-ichi

2-ni

3-san

4-yon/shi

5-go

6-roku

7-nana/shichi

8-hachi

9-kyuu

10-jyuu

11-jyuu-ichi

12-jyuu-ni

20-ni-jyuu

23-ni-jyuu-san

30-san-jyuu

40-yon-jyuu

100-hyaku

Just notice the pattern. It's actually very easy.