- Today, we will be learning about permutations and combinations!
- What's the difference between a permutation and combination?
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- Is this a hard lesson?
- Nonsense, this lesson is not hard. A permutation is where the order matters for the ranging of objects.
- The equation for permutations are nPr= P!/(n-r)!.
- For example, your school is competing in a track team with 12 other teams. Find the different possibilities of your team winning first or second place.
- See order matters here! First you know n=12 and r=2. Now set up the equation. 12P2= 12!/(12-2)!
- You can simplify to 12*11, instead of doing all the math.
- So you get 12! which translates to 12*11*10*9*8 etc. 12-2=10! Your equation is 12!/10!
- Your final answer is 132 ways.
- It makes sense!
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- So n is the objects where r is the time. r is less than or equal to n! Now what is a combination?
- Perfect, lets start with combinations now! Combination is a collection of objects, and order doesn't matter!!!!
- The formula is nCr= n!/(n-r)!*r!

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