

NCERT Solutions for Class 12 Maths Chapter 3 Miscellaneous Exercise
Solve The Following Questions NCERT Solutions for Class 12 Maths Chapter 3 Exercise 3.1 Matrices:
Question 1. In the matrix A =
, write:
(i) The order of the matrix.
(ii) The number of elements.
(iii) Write the elements
Solution :
(i) There are 3 horizontal lines (rows) and 4 vertical lines (columns) in the given matrix A.
Therefore, Order of the matrix is 3 x 4.
(ii) The number of elements in the matrix A is 3 x 4 = 12.
(iii) a
13
Element in first row and third column = 19
a
21
Element in second row and first column = 35
a
33
Element in third row and third column = -5
a
24
Element in second row and fourth column = 12
a
23
Element in second row and third column = 5/2
NCERT Solutions for Class 12 Maths Chapter 3 Exercise 3.2
Question 2. If a matrix has 24 elements, what are possible orders it can order? What, if it has 13 elements? Solution : We know that if a matrix is of the order m × n, it has mn elements. Thus, to find all the possible orders of a matrix having 24 elements, we have to find all the ordered pairs of natural numbers whose product is 24. The ordered pairs are: (1, 24), (24, 1), (2, 12), (12, 2), (3, 8), (8, 3), (4, 6), and (6, 4) Hence, the possible orders of a matrix having 24 elements are: 1 × 24, 24 × 1, 2 × 12, 12 × 2, 3 × 8, 8 × 3, 4 × 6, and 6 × 4 (1, 13) and (13, 1) are the ordered pairs of natural numbers whose product is 13. Hence, the possible orders of a matrix having 13 elements are 1 × 13 and 13 × 1.NCERT Solutions for Class 12 Maths Chapter 3 Exercise 3.3
Question 3. If a matrix has 18 elements, what are the possible orders it can have? What if has 5 elements? Solution : We know that if a matrix is of the order m × n, it has mn elements. Thus, to find all the possible orders of a matrix having 18 elements, we have to find all the ordered pairs of natural numbers whose product is 18. The ordered pairs are: (1, 18), (18, 1), (2, 9), (9, 2), (3, 6,), and (6, 3) Hence, the possible orders of a matrix having 18 elements are: 1 × 18, 18 × 1, 2 × 9, 9 × 2, 3 × 6, and 6 × 3 (1, 5) and (5, 1) are the ordered pairs of natural numbers whose product is 5. Hence, the possible orders of a matrix having 5 elements are 1 × 5 and 5 × 1.NCERT Solutions for Class 12 Maths Chapter 3 Exercise 3.4
Question 4. Construct a 2 x 2 matrix A = [a ij ] whose elements are given by: (i)
(ii) a
ij
= i/j
(iii)
Solution :
(i)
(ii)
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(iii)
(ii) a
ij
= 2i - j
Solution :
(i)
(ii)
| NCERT Solutions for Class 12 Maths Chapter 2 Exercise 2.1 | NCERT Solutions for Class 12 Maths Chapter 2 Exercise 2.2 |
| NCERT Solutions for Class 12 Maths Chapter 2 Miscellaneous Exercise | |
(ii)
(iii)
Solution :
(i)Given:
As the given matrices are equal, their corresponding elements are also equal.
Comparing the corresponding elements, we get:
x = 1, y = 4 = z = 3
(ii)
As the given matrices are equal, their corresponding elements are also equal.
Comparing the corresponding elements, we get:
x + y = 6, xy = 8 and 5 + z = 5
Now, 5 + z = 5 ⇒ z = 0
We know that:
(x - y)
2
= (x + y)
2
- 4xy
⇒ (x - y)
2
= 36 - 32 = 4
⇒x - y = ± 2
Now, when x - y = 2 and x + y = 6 , we get x = 4, y = 2
When x - y = -2 and x + y = 6, we get x = 2, y = 4
∴ x = 4, y = 2, and z = 0, or x = 2, y = 4 and z = 0
(iii)
Question
7. Find the values of a,b, c and d from the equation
.
Solution :
As the two matrices are equal, their corresponding elements are also equal.
Comparing the corresponding elements, we get:
a − b = −1 … (1)
2a − b = 0 … (2)
2a + c = 5 … (3)
3c + d = 13 … (4)
From (2), we have:
b = 2a
Then, from (1), we have:
a − 2a = −1
⇒ a = 1
⇒ b = 2
Now, from (3), we have:
2 ×1 + c = 5
⇒ c = 3
From (4) we have:
3 ×3 + d = 13
⇒ 9 + d = 13 ⇒ d = 4
∴a = 1, b = 2, c = 3, and d = 4
Question
8. A = [a
ij
]
m x n
is a square matrix if:
(A) m < n (B) m > n (C) m = n (D) None of these
Solution :
It is known that a given matrix is said to be a square matrix if the number of rows is equal to the number of columns. A = [a
ij
]
m x n
option (C) is correct.
Question
9. Which of the given values of x and y make the following pairs of matrices equal:
(B) Not possible to find
Solution :
We find that on comparing the corresponding elements of the two matrices, we get two different values of x , which is not possible.
Hence, it is not possible to find the values of x and y for which the given matrices are equal.
Therefore, option (B) is correct.
Question
10. The number of all possible matrices of order 3 x 3 with each entry 0 or 1 is:
(A) 27
(B) 18
(C) 81
(D) 512
Solution :
The correct answer is D.
The given matrix of the order 3 × 3 has 9 elements and each of these elements can be either 0 or 1.
Now, each of the 9 elements can be filled in two possible ways.
Therefore, by the multiplication principle, the required number of possible matrices is 2
9
= 512
