Write the number of all possible matrices of order with each entry 1 or 2.
Any mather of shall have 6 elements which are to be filled by either 1 or 2 (ie. in 2 ways). So total numbers of all possibie matrices are same as the number of ways
of filling these entries 1 or 2 in 6 places.
Hence total number of matrices are
or 64.