How to generate a different 4-digit number by using only these (1, 2, 4, 6, 7, and 9) numbers - Quora
How many numbers can be formed from 1, 2, 3, 4, 5 (without repetition), when the digit at the unit's place must be greater than that in the ten's place? - Quora
![The total number of 5 digit numbers, formed by using the digits 1, 2, 3, 5, 6, 7 without repetition, - YouTube The total number of 5 digit numbers, formed by using the digits 1, 2, 3, 5, 6, 7 without repetition, - YouTube](https://i.ytimg.com/vi/lFLx7XyENi8/mqdefault.jpg)