One integer in every ten has a 4 in the units position. That gives 4s in the units position (in the integers from 1 to ). Ten integers in every hundred have a 4 in the tens position (in other words, each of the integers ending in 40, 41, ..., 49). That gives (again) 4s in the tens position. And so on. There will be a total of 4s in the hundreds position, in the thousands position, in fact in each of the six positions in a six-digit number. So the total number of 4s that you would have to write, if you wrote down all the integers from 1 to a million would be 600,000.