5 X 5
The dimensions of a matrix number of rows and columns of that matrix. If it is as an (read as by it means that it has number of rows and number of columns.
In the given problem, the rows and columns are 5. So, we write it is a matrix. We call it a Square matrix, since the number of rows equals the number of columns.
hans did not square the 40-unit side; he merely multiplied it by 2. incorrect.