If a matrix contians 3 columns and 5 rows, find the order of the matrix.

If the number of rows and the number of columns of a matrix are equal and the matrix contains 25 elements, then the order of the matrix is _______

If the number of rows and that of columns of a matrix are equal and the matrix contains 16 elements, then the order of the matrix is _______

If a matrix contain 5 rows and 3 columns, then the number of elements of the matrix is _____

A matrix contains 2 rows and 4 columns and every element in the matrix is 1, then find the matrix.

If A is a matrix of order 3xx4 and B is a matrix of order 4xx3 , find the order of the matrix (AB).