challenge puzzle 1 to 100…. how many 9s do you see? comment your answer

Try to write 1 to 100 and you can easily count no of 9 s in between 1 to 100

but there is a logic behind in it try and comment your answer otherwise scroll below to see the answer

one 9 in every 10s (like 9, 19, 29, etc) => 10

extra 10 9s in 90 – 99 => 10

thus total 20