NCERT Solutions for class 12 Maths | Chapter 3 - Matrices

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Questions
1 If A = Class 12 Matrices then find value of α for which A² = B is
A 1
B -1
C 4
D None of these

Answer:None of these
2 If A = Class 12 Matrices then A8 – 28 (A – I)
A I – A
B A
C I + A
D A – 2I

Answer:2I – A
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3 If A = Class 12 Matrices then A2 – 5A is equal to
A 2I
B 3I
C -2I
D null matrix

Answer:2I
4 If A = Class 12 Matrices

B = Class 12 Matrices

then A – B equal to

A I
B O
C 1
D 3/2 |

Answer:3/2 |
5 If Class 12 Matrices then find the value of x, y, z and w respectively
A 2, 2, 3, 4
B 2, 3, 1, 2
C 3, 3, 0, 1
D None of these

Answer:2, 2, 3, 4
6 If A = Class 12 Matrices then the value of x is
A 3
B ±3
C ±6
D 6

Answer:3
7 If A = Class 12 Matrices then A² – 5A – 7I is
A zero matrix
B a diagonal matrix
C identity matrix
D None of these

Answer:a diagonal matrix
8 If A = Class 12 Matrices then |2A| =
A 2|A|
B 4|A|
C 8|A|
D None of these

Answer:4|A|
9 Class 12 Matrices
A α = a² + b², β = ab
B α = a² + b², β = 2ab
C α = a² + b², β = a² – b²
D α = 2ab, β = a² + b²

Answer:α = a² + b², β = 2ab
10 If Class 12 Matrices then the value of x, y is
A 3, 1
B 2, 3
C 2, 4
D 3, 3

Answer:2, 3
11 If P is of order 2 x 3 and Q is of order 3 x 2, then PQ is of order
A 2 x 3
B 2 x 2
C 3 x 2
D 3 x 3

Answer:2 x 2
12 If a matrix has 24 elements then the number of possible order it can have, is
A 6
B 8
C 12
D 16

Answer:8
13 If A and B are two matrices such that both AB and BA are defined, then
A A and B can be any two matrices .
B A and B are not square matrices not necessarily of the same order.
C A and B are square matrices of the same order .
D number of columns of A = number of rows of B .

Answer:A and B are not square matrices not necessarily of the same order.
14 If A is an orthogonal matrix then AT is a/an
A identity matrix
B null matrix
C orthogonal matrix
D scalar matrix

Answer:orthogonal matrix
15 If A = [3 4 7 -1] [1 6 7 2] [9 8 6 4]

then the order of the matrix is

A 4 * 3
B 3 * 4
C 3 * 3
D 4 * 4

Answer:3 * 4
16 If 2[3 4] + [1 y] = [7 0] [5 x] [0 1] [10 5] then the value of x - y is
A 8
B 10
C -8
D -10

Answer:10
17 If A = [ 2 -3 -1 4] then the matrix B such that 2A + 3B = 0 is
A [4/3 2 2/3 -8/3]
B [-4/3 2 2/3 8/3]
C [-4/3 2 2/3 -8/3]
D [-4/3 2 -2/3 -8/3]

Answer:[-4/3 2 2/3 -8/3]
18 If A is a skew symmetric matrix of order 3, then the value of determinant A is
A 0
B 1
C -1
D None of these

Answer:0
19 If A is a square matrix, then A is symmetric iff
A A2 = A
B A2 = I
C At = A
D At = - A

Answer:At = A
20 If A is any square matrix, then
A A + At is symmetric
B A - At is symmetric
C AAt is scew symmetric
D none of these

Answer:A + At is symmetric

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