In a town, the car plate numbers contain only three or four digits, not containing the dit 0. What is the maximum numbers of cars that can be numbered?

In a town the car plate numbers contain only three or four digits, not containing the digit 0. The maximum number of cars that can be numbered is

The system that contains the maximum number of atoms is

The number of 3- digit numbers containing the digit 7 exactly once :

The number of 3- digit numbers containing the digit 7 exactly once :

How many six-digit numbers contain exactly four different digits?

The maximum number of electrons that d-orbital can contain is

How many three digit numbers can be written using digits 4,6, and 9 without repeating the digits? i) What is the probability that the numbers are odd numbers? ii) What is the probability that the numbers are even numbers?