The FX-991ES offers simple matrix operations like basic arithmetic, plus the slightly more complex operations determinant and inversion. Furthermore, it is limited to matrices with a maximum size of three rows and three columns.
The rank of a matrix is defined as the number of linearly independent row or column vectors. You can perform a simple partial test for square matrices by calculating the determinant of the matrix:
- Enter the matrix into matrix variable MatA.
- Press [SHIFT]   [SHIFT]   [)] [=]
The display now should show det(MatA) and the determinant of the matrix in the result. If the determinant is not
0, the rank of the matrix equals the dimension of the matrix, otherwise the rank is less than the dimension.
Unfortunately, this is all support the calculator offers. For small matrices (i.e. 4x4 or smaller), you should familiarize yourself with the Gau? Elimination Method algorithm for solving linear equation systems. It is a two-step procedure where a matrix first is converted to its row echelon form, and second to row canonical form to solve the LES.
You need to follow the algorithm only through the first part, the number of non-zero rows after this step equals the rank of the matrix. With a little exercise you will be able to do it faster on paper than trying to do it with your calculator only.
For larger matrices I suggest to use a PC with more powerful math software (Maple, Mathematica, ...) or, if you know some basic computer programming, just write the necessary program yourself, which is also a very good exercise both in programming and understanding the algorithm.