Thread: Matrices and permutations

I've been going over some review for some placement test I have to take, I've never done anything with Matrices (I think that's the plural for Matrix, haha) and I'm ruuuuusty on solving permutations:


I don't think these are particularly difficult, I'm just slow in the subjects..Thanks for anyone who can clarify

Originally Posted by doomgaze

I've been going over some review for some placement test I have to take, I've never done anything with Matrices (I think that's the plural for Matrix, haha) and I'm ruuuuusty on solving permutations:


I don't think these are particularly difficult, I'm just slow in the subjects..Thanks for anyone who can clarify

means the determinant of a matrix. For a 2x2 matrix, that is a matrix with 2 rows and 2 columns:


the determinant is .

And if the determinant is zero, the matrix does not have an inverse.

(34) if you are considering the ways in which the committee of 3 people is chosen without order

Originally Posted by harish21

(34) if you are considering the ways in which the committee of 3 people is chosen without order

so you take the total amount of people then divide (total - the # of people per group) ?

Originally Posted by doomgaze

so you take the total amount of people then divide (total - the # of people per group) ?

We are NOT taking the total amount/number of people here. The exclamation mark ! that you see after the numbers is called factorial.

7!= 1*2*3....*7
3!= 1*2*3
4!= 1*2*3*4


To know how this formula comes, you need to study permutations and combinations..Google it.

This link might be useful

Originally Posted by harish21

We are NOT taking the total amount/number of people here. The exclamation mark ! that you see after the numbers is called factorial.

7!= 1*2*3....*7
3!= 1*2*3
4!= 1*2*3*4


To know how this formula comes, you need to study permutations and combinations..Google it.

This link might be useful

Yeah I knew they were factorials, I guess I just didn't express it when I was trying to explain what I thought you said.

Thanks for the link, it is clearing things up.