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**eelety****Member**- Registered: 2010-09-16
- Posts: 1

I have four problems where I have the find the number of permutations. Could any help me in figuring out these types of algebra problems. Subject Algebra I, grade 10.

#1. 7P3

#2 7P7

#3. 8P4

#4. 5P0

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**bobbym****bumpkin**- From: Bumpkinland
- Registered: 2009-04-12
- Posts: 109,606

Hi eelety;

Welcome to the forum!

1) 7P3 Take the first number which is 7 and count down by 1, the second number 3 times. Then multiply.

2) 7P7, Take the first number 7 and count down by 1, 7 times. Then multiply.

Now you try 8P4.

**In mathematics, you don't understand things. You just get used to them.****If it ain't broke, fix it until it is.**** Always satisfy the Prime Directive of getting the right answer above all else.**

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**soroban****Member**- Registered: 2007-03-09
- Posts: 452

Edit: That was really *stupid!* . . . I used the *Combination* formula is all of these . . . *blush*

. .

.

*Last edited by soroban (2010-09-17 05:15:21)*

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**mathsyperson****Moderator**- Registered: 2005-06-22
- Posts: 4,900

That's the formula for Combinations, not Permutations. The difference is that with permutations, order is important. This means that, for example, when choosing all the members of a set, there are many ways of doing so instead of just one.

The formula for permutations is:

Why did the vector cross the road?

It wanted to be normal.

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