Counting is the foundation stone of Mathematics and is one of the most basic things that we learn. When dealing with larger data, making use of permutation and combination makes it convenient for us. In this chapter, we will learn about the permutation and combination formula and some fundamental principles of counting. Let’s start.

**Q1. State some difference between permutation and combination?**

**A1.** Permutation is the order of the elements, on the other hand, combination do not have an order of the element. Besides, the difference between combination and permutation is ordering.

**Q2. Where we use permutation and combination?**

**A2.** Permutation is used for lists (order matters) and combination for groups (order doesn’t matter). Besides, a famous joke for the difference is that a combination lock should really be called a permutation lock. In addition, the order you put in the numbers of lock matters.

**Q3. What is the formula of combination?**

**A3.** Combination is the way to calculate the total outcomes of an event where the order of the outcomes does not matter. In addition, for calculating combinations, we will use the formula nCr = n! / r! × (n-r)!. Here n represents the total number of items and r represents the number of items being chosen.

**Q4. How many combinations are possible with the number 1, 2, 3, and 4?**

**A4.** A total of 64 combinations are possible by the number 1, 2, 3, and 4. Some examples are:

1

2

3

4

1, 2

1, 3

1, 4

2,1

And so on.