How many times does the digit 9 appear in the list of all integers from 1 to 5000? (The number 99, for example, is counted twice, because 9 appears two times in it.)
From 1 to 100 ==20 From 101 to 1000 ==280 [20 + 280] * 5 ==1,500 - "9s" between 1 and 5,000.
