Factorials & the Counting Principle
Factorial और counting principle
title
Factorials & the Counting Principle
- Permutation & Combination
- Factorials & the Counting Principle
नमस्ते दोस्तों, कैसे हैं आप सब? चलिए आज की class शुरू करते हैं। आज की class में समझेंगे — Factorial और counting principle। बिलकुल zero से, एकदम आसान भाषा में। चलिए शुरू करते हैं!
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Interactive — learn by doing. Drag, tap and explore to build the intuition.
Does the order matter?
Pick r from n. If arrangement matters (a race podium) use permutations; if only the group matters (a team) use combinations.
ⁿPᵣ = 5! / (5−3)!
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order matters — arrangements
ⁿCᵣ = ⁿPᵣ / 3!
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order ignored — selections
💡 Every selection of 3 can be arranged 3! ways, so ⁿPᵣ is exactly 3! times ⁿCᵣ.