Question: how many 5 digit combinations are there using 1-9?
Answer: So, the number of ways we can fill the 5th place is 9. For the 4th place, we can have any digit from 0–9. Same goes for the 3rd, 2nd as well as the One's place. Finally we can multiply them and get your answer which is 9*10*10*10*10 which results in 90000.