# Counting Techniques

## Fundamental Principle of Counting

If there are $m$ ways to do a task and $n$ ways to do another task, the number of ways to do the first then the second task is $m \times n$.

**In this video**

- How many 5-digit numbers can be made out from the digits 4, 6, 7, 8 and 9?
- In how many ways can 5 students be seated on a bench?
- Three-digit numbers are to be made out from the digits 0, 1, 2, 3, 4, 5, 6, and 7. Repetition of digit is not allowed.

- How many such numbers can be made?
- From 3-a, how many are greater than 400?
- From 3-a, how many are even numbers?
- From 3-a, how many are odd numbers greater than 300?

- How many ways are there to label the four corners of a square with letters from English alphabet such that...

- each corner gets a different letter?
- adjacent corners get different letters?

- In how many ways can 6 individuals be seated in a round table with 6 chairs?

- Suppose 2 persons wanted to be seated side by side, in how many ways can they do it?
- In how many ways can these 6 individuals arrange themselves if 2 among them refuse to sit together?