ADV001 · Advanced mathematics · Classes 11–12 + B.Tech
Permutations
A permutation is an arrangement where order matters. The number of ways to arrange r items chosen from n is ⁿPᵣ = n!/(n − r)!.
ⁿPᵣPermutations
📐 Formula
ⁿPᵣ = n! / (n − r)!
✏️ Worked example
Choosing a captain and a vice-captain from 5 players: ⁵P₂ = 5 × 4 = 20.
🌍 Where it is used
Passwords, race positions, seating plans.
❓ Quick check
Ways to arrange 3 books on a shelf?
🏋️ Practice
Easy⁶P₂ = ?
Answer: 30
MediumArrangements of the letters of CAT?
Answer: 6
Challenge4-digit PINs with all digits different?
Answer: 5040