# Thread: Find null and rank.

1. ## Find null and rank.

If dim Null A of a 4 x 5 matrix A is 2, find rank A, dim Col A, dim Row A, and rank $A^T$

So far:

I know that dim null A + rank A = 5, so rank A is equal to 3, and dim Col A is equal to rank A, so it is also 3. But what of the other two? Thanks.

2. There's a theorem that row rank is always the same as column rank, from which it immediately follows that the rank of a matrix is the same as the rank of the transpose matrix.