Permutations and Combinations — Class 11 Mathematics
Core Idea
Use permutations when order matters and combinations when selection order does not. This distinction is the key to choosing the correct formula.
Worked Examples
Arrangements of 5 different books on a shelf: 5!=120.
Ways to choose 3 students from 8: ⁸C₃=8!/(3!5!)=56.
Ways to arrange 3 students selected from 8: ⁸P₃=8!/(5!)=336.
Explained MCQs
- Choosing a committee uses combination because order is irrelevant.
- Arranging letters in a row uses permutation.
- ⁶C₂=15.
Practice
- How many 4-digit numbers can be formed from 1,2,3,4,5 without repetition?
- From 10 players, how many teams of 4 can be selected?