
58 MATHEMATICS
respectively. Similarly, in the second arrangement, the entries in the first row represent
the number of notebooks possessed by Radha, Fauzia and Simran, respectively. The
entries in the second row represent the number of pens possessed by Radha, Fauzia
and Simran, respectively. An arrangement or display of the above kind is called a
matrix. Formally, we define matrix as:
Definition 1
A
matrix is an ordered rectangular array of numbers or functions. The
numbers or functions are called the elements or the entries of the matrix.
We denote matrices by capital letters. The following are some examples of matrices:
,
,
In the above examples, the horizontal lines of elements are said to constitute, rows
of the matrix and the vertical lines of elements are said to constitute, columns of the
matrix. Thus A has 3 rows and 2 columns, B has 3 rows and 3 columns while C has 2
rows and 3 columns.
3.2.1 Order of a matrix
A matrix having m rows and n columns is called a matrix of order m × n or simply m × n
matrix (read as an m by n matrix). So referring to the above examples of matrices, we
have A as 3 × 2 matrix, B as 3 × 3 matrix and C as 2 × 3 matrix. We observe that A has
3 × 2 = 6 elements, B and C have 9 and 6 elements, respectively.
In general, an m × n matrix has the following rectangular array:
or A = [a
ij
]
m × n
, 1≤ i ≤ m, 1≤ j ≤ n i, j ∈ N
Thus the i
th
row consists of the elements a
i1
, a
i2
, a
i3
,..., a
in
, while the j
th
column
consists of the elements a
1j
, a
2j
, a
3j
,..., a
mj
,
In general a
ij
, is an element lying in the i
th
row and j
th
column. We can also call
it as the (i, j)
th
element of A. The number of elements in an m × n matrix will be
equal to mn.