In this article, we will discuss the basic concepts of Permutation & Combination and formulas required for solving problems on the same. This topic is covered in all competitive exams, so you cannot afford to take the risk of avoiding it. After reading this article, you will become familiar with the basic concepts of permutation and combination.

**Permutation f****ormula:**Permutation is defined as arrangement of r things that can be done out of total n things. This is denoted bywhich is equal to n!/(n-r)!^{n}P_{r }**Combination formula**- Combination is defined as selection of r things that can be done out of total n things. This is denoted by
^{n}C_{r }which is equal to n!/r!(n-r)! - As per the Fundamental Principle of Counting, if a particular thing can be done in
*m*ways and another thing can be done in*n*ways, then either one of the two can be done in*m +**n*ways and both of them can be done in*m ×**n*ways.

- Combination is defined as selection of r things that can be done out of total n things. This is denoted by

Or some logic can be applied: Every question has 2 options, either it is attempted or not. Going ahead with this logic, since there are 10 questions, and each question has 2 options, so total number of cases = 2^{10}= 1024. But this count includes one case in which no question is attempted. This is the violation of the information given. So this case needs to be subtracted. Hence the total number of cases would be 1024 - 1 = 1023.

Suggested Action:

- In this article, you learned the basic concepts and formulae useful for solving questions on Permutations & Combinations.
- Statement questions are primarily designed to test your understanding to frame an equation and then use formulae on it.