As far as I know There are two kinds of numbering system 1) Sino-Korean 2) Native Korean and both are used at the same time. let's start with Sino-Korean 1- 일 2- 이 3- 삼 4- 사 5- 오 6- 육 7- 칠 8- 팔 9- 구 10- 십 to indicate the tens we use ( 십 ) 11- 십일 20- 이십 21- 이십일 = 이십(20) + 일 (1) and so on ^^ @cici I hope that you can read Hangul because I'm not familiar with Korean romanization ,,,If not maybe Ryan can help!