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JEE • MATHEMATICS • MATRICES

Matrices practice · Mixed difficulty

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841 Easy
841 of 995
Understanding +4 | -1
If AA is any m×nm \times n matrix such that ABAB and BABA are both defined., then BB is an
View answer and explanation
Correct option: B
n×mn \times m matrix
Option B (n×mn \times m matrix) is correct because for AB and BA to be defined, B must have n rows and m columns.
842 Easy
842 of 995
Application +4 | -1
Let AA be an orthogonal non-singular matrix of order nn, then the determinant of matrix 'A−In′    ie,  ∣A−In∣A - {I'_n}\;\,\,ie,\;\left| {A - {I_n}} \right| is equal to
View answer and explanation
Correct option: C
∣A∣∣In−A∣\left| A \right|\left| {{I_n} - A} \right|
Option C (∣A∣∣In−A∣\left| A \right|\left| {{I_n} - A} \right|) is correct because it follows from the properties of orthogonal matrices and determinants.
843 Easy
843 of 995
Analyzing +4 | -1
The existence of the unique solution of the system of equations
x+y+z=λx+y+z=\lambda

5x−y+μz=105 x-y+\mu z=10

2x+3y−z=62 x+3 y-z=6
depends on
View answer and explanation
Correct option: A
μ\mu only
Option A is correct because the existence of a unique solution depends on the determinant of the coefficient matrix being non-zero, which is determined by μ\mu only.
844 Medium
844 of 995
Analyzing +4 | -1
Let the matrix A=∣010001100∣A=\left|\begin{array}{lll}0 & 1 & 0 \\ 0 & 0 & 1 \\ 1 & 0 & 0\end{array}\right| and the matrix B0B_0 =A49+2A98=A^{49}+2 A^{98}. If Bn=Adj⁡(Bn−1)B_n=\operatorname{Adj}\left(B_{n-1}\right) for all n≥1n \geq 1, then det⁡(B4)\operatorname{det}\left(B_4\right) is equal to :
View answer and explanation
Correct option: C
3323^{32}
Option C (3323^{{32}}) is correct because after simplifying the matrix operations and using the properties of adjoint and determinants, the final determinant can be calculated.
845 Easy
845 of 995
Application +4 | -1
Let A=(aij)A=\left(a_{i j}\right) be a 3×33 \times 3 matrix whose determinant is 5. The determinant of the matrix B=(2i−jaij)B=\left(2^{i-j} a_{i j}\right) is
View answer and explanation
Correct option: A
5
Option A (5) is correct because the determinant of matrix B is equal to the determinant of matrix A.
846 Easy
846 of 995
Analyzing +4 | -1
The system of equations −kx+3y−14z=25,    −15x+4y−kz=3,   −4x+y+3z=4- kx + 3y - 14z = 25,\,\,\,\, - 15x + 4y - kz = 3,\,\,\, - 4x + y + 3z = 4 is consistent for all k in the set
View answer and explanation
Correct option: D
R−{−11,11}R - \{ - 11,11\}
Option B (R−{−11,13}R - \{ - 11,13\}) is incorrect. Option D (R−{−11,11}R - \{ - 11,11\}) is correct because the system is consistent when the determinant of the coefficient matrix is non-zero, which occurs for all k except ±11.
847 Easy
847 of 995
Analyzing +4 | -1
For what value of λ\lambda, the system of equations
x+y+z=6x+y+z=6

x+2y+3z=10x+2 y+3 z=10

x+2y+λz=12x+2 y+\lambda z=12
is inconsistent?
View answer and explanation
Correct option: D
λ=3\lambda=3
Option D is correct because the system is inconsistent when λ=3\lambda = 3, leading to a contradiction in the equations.
848 Easy
848 of 995
Application +4 | -1
Let A=[0α00]A=\left[\begin{array}{ll}0 & \alpha \\ 0 & 0\end{array}\right] and (A+I)50−50A=[abcd](A+I)^{50}-50 A=\left[\begin{array}{ll}a & b \\ c & d\end{array}\right], find a+b+c+da+b+\mathrm{c}+d.
View answer and explanation
Correct option: A
2
Option A (2) is correct because since A2=0A^2 = 0, (A+I)50=I+50A(A+I)^{50} = I + 50A. Therefore, (A+I)50−50A=I(A+I)^{50} - 50A = I, which means a=1,b=0,c=0,d=1a=1, b=0, c=0, d=1, and a+b+c+d=2a+b+c+d = 2.
849 Easy
849 of 995
Understanding +4 | -1
If AA is any square matrix then which of the following is not symmetric?
View answer and explanation
Correct option: B
A−A′A-A^{\prime}
Option B (A−A′A-A^{\prime}) is correct because the transpose of (A−A′)(A-A^{\prime}) is (A′−A)(A^{\prime}-A), which is the negative of (A−A′)(A-A^{\prime}), making it skew-symmetric, not symmetric.
850 Easy
850 of 995
Analyzing +4 | -1
If AA is a real skew-symmetric matrix such that A2+I=OA^2+I=O, then
View answer and explanation
Correct option: D
A is a skew-symmetric matrix of even order with ∣A∣=1|A|=1
The correct answer is A is a skew-symmetric matrix of even order with ∣A∣=1|A|=1 because A2+I=0A^2 + I = 0 implies ∣A∣=1|A| = 1 and A must be of even order since it's a real skew-symmetric matrix.
851 Easy
851 of 995
Application +4 | -1
Elements of a matrix AA of order 10×1010 \times 10 are defined as aij=ωi+ja_{i j}=\omega^{i+j} (where ω\omega is cube root of unity), then trace (A)(A) of the matrix is
View answer and explanation
Correct option: D
None of these
Option D (None of these) is correct because the trace of the matrix A simplifies to ω2\omega^2, which is not among the given options.
852 Easy
852 of 995
Understanding +4 | -1
Let A=(abcd)A=\left(\begin{array}{ll}a & b \\ c & d\end{array}\right), where a,b,c,d∈Ra, b, c, d \in {R}. If ∣a∣,∣b∣,∣c∣,∣d∣≤k|a|,|b|,|c|,|d| \leq k, where k>0k > 0, then
View answer and explanation
Correct option: C
det⁡(A)≤2k2\operatorname{det}(A) \leq 2 k^2
Option C (det⁡(A)≤2k2\operatorname{det}(A) \leq 2 k^2) is correct because the determinant of A, which is ad−bcad-bc, is bounded by ∣ad∣+∣bc∣|ad| + |bc|, and since ∣a∣,∣b∣,∣c∣,∣d∣≤k|a|, |b|, |c|, |d| \leq k, the determinant is at most 2k22k^2.
853 Medium
853 of 995
Application +4 | -1
If the product of nn matrices [1101][1201][1301]…[1n01]\left[\begin{array}{ll}1 & 1 \\ 0 & 1\end{array}\right]\left[\begin{array}{ll}1 & 2 \\ 0 & 1\end{array}\right]\left[\begin{array}{ll}1 & 3 \\ 0 & 1\end{array}\right] \ldots\left[\begin{array}{ll}1 & n \\ 0 & 1\end{array}\right] is equal to the matrix [137801]\left[\begin{array}{cc}1 & 378 \\ 0 & 1\end{array}\right], then the value of nn is equal to
View answer and explanation
Correct option: A
27
Option A (27) is correct because the product of the matrices results in a matrix of the form [1sum01]\begin{bmatrix} 1 & sum \\ 0 & 1 \end{bmatrix}, where the sum is 1+2+3+...+n=n(n+1)21+2+3+...+n = \frac{n(n+1)}{2}. Setting this equal to 378 and solving for n gives n=27.
854 Easy
854 of 995
Application +4 | -1
If A=[2−3−41]A = \left[ {\begin{array}{cccccccccccccccccccc} 2&{ - 3}\\ { - 4}&1 \end{array}} \right], then adj\mathrm{adj} (3A2+12A)\left( {3{A^2} + 12A} \right) is equal to
View answer and explanation
Correct option: B
[51638472]\left[ {\begin{array}{cccccccccccccccccccc} {51}&{63}\\ {84}&{72} \end{array}} \right]
Option B ([51638472]\left[ {\begin{array}{cccccccccccccccccccc} {51}&{63}\\{84}&{72} \end{array}} \right]) is correct because it is the adjugate of the matrix 3A2+12A3{A^2} + 12A calculated correctly.
855 Easy
855 of 995
Application +4 | -1
The inverse of the matrix [5−231]\left[ {\begin{array}{cccccccccccccccccccc} 5&{ - 2}\\ 3&1 \end{array}} \right] is
View answer and explanation
Correct option: A
111[1          2−3        5]\frac{1}{{11}}\left[ {\begin{array}{cccccccccccccccccccc} {1\;\;\;\;\;2}\\ { - 3\;\;\;\;5} \end{array}} \right]
Option A (\frac{1}{{11}}\left[ {\begin{{array}}{{{*{20}{c}}}} {1\;\;\;\;2}\\ { - 3\;\;\;5} \end{{array}}} \right]\frac{1}{{11}}\left[ {\begin{{array}}{{{*{20}{c}}}} {1\;\;\;\;2}\\ { - 3\;\;\;5} \end{{array}}} \right]) is correct because it is the correctly computed inverse of the given 2x2 matrix.
856 Easy
856 of 995
Application +4 | -1
If kk is a scalar and II is a unit matrix of order 3, then adj (kI)\left( {kI} \right) is equal to
View answer and explanation
Correct option: B
k2I{k^2}I
Option B (k2I{k^2}I) is correct because adj(kI)=kn−1I(kI) = k^{n-1}I where n is the order of the matrix. In this case, n=3, so adj(kI)=k2I(kI) = k^2I.
857 Medium
857 of 995
Analyzing +4 | -1
Let A{A} and B{B} be two matrices such that A=[aij]2×3=[x123x−114x2+1]A=\left[a_{i j}\right]_{2 \times 3}=\left[\begin{array}{ccc}x & 1 & 2 \\ 3 x & -1 & \frac{1}{4 x^2+1}\end{array}\right] and B=[bij]3×2=[1x21x2x23x]B=\left[b_{i j}\right]_{3 \times 2}=\left[\begin{array}{cc}\frac{1}{x^2} & \frac{1}{x} \\ 2 x & 2 \\ 3 & x\end{array}\right] where x>0x > 0. If matrix CC is defined as C=[cij]2×2C=\left[c_{i j}\right]_{2 \times 2}, where cij=∑r=13airbrj,∀1≤i,j≤2c_{i j}=\sum\limits_{{r=1}}^3 a_{i r} b_{r j}, \forall 1 \leq i, j \leq 2, then the minimum value of Δ(x)=∑1≤i≤j≤2cij\Delta(x)=\sum\limits_{{1 \leq i \leq j \leq 2}} c_{i j} is
View answer and explanation
Correct option: A
574\frac{57}{4}
Option A (574\frac{57}{4}) is correct because after calculating the matrix C and summing its elements, the minimum value of the resulting expression is 574\frac{57}{4}.
858 Easy
858 of 995
Analyzing +4 | -1
Let A=[i−i−ii],  i=−1A = \left[ {\begin{array}{cccccccccccccccccccc} i&{ - i}\\ { - i}&i \end{array}} \right],\,\,i = \sqrt { - 1}. Then the system of linear equations A8[xy]=[864]{A^8}\left[ {\begin{array}{cccccccccccccccccccc} x\\ y \end{array}} \right] = \left[ {\begin{array}{cccccccccccccccccccc} 8\\ {64} \end{array}} \right] has:
View answer and explanation
Correct option: A
No solution
Option A (No solution) is correct because the equations derived from the matrix equation are inconsistent, leading to no solution.
859 Medium
859 of 995
Application +4 | -1
If AA is a square matrix of order n×nn \times n and kk is a scalar, then adj (kA)\left( {kA} \right) is equal to
View answer and explanation
Correct option: C
kn−1  adj  A{k^{n - 1}}\;\mathrm{adj\;}A
Option C, kn−1  adj  A{k^{n - 1}}\;\mathrm{adj\;}A, is correct because it represents the correct relationship between adj(kA) and adj(A) for a square matrix of order n.
860 Medium
860 of 995
Application +4 | -1
If A=[101/21]A=\left[\begin{array}{lr}1 & 0 \\ 1 / 2 & 1\end{array}\right], then A50A^{50} is
View answer and explanation
Correct option: D
None of these
None of these is the correct answer. The correct answer is [10251]\left[\begin{array}{ll}1 & 0 \\25 & 1\end{array}\right], which is obtained by induction.
861 Easy
861 of 995
Application +4 | -1
Let A=[3    52    0]A = \left[ {\begin{array}{cccccccccccccccccccc} {3\;\;5}\\ {2\;\;0} \end{array}} \right] and   B=[1            170       −10],  \;B = \left[ {\begin{array}{cccccccccccccccccccc} {1\;\;\;\;\;\;17}\\ {0\,\,\,\;\; - 10} \end{array}} \right],\; then   ∣AB∣\;\left| {AB} \right| is equal to
View answer and explanation
Correct option: B
100
Option B is correct because calculating the product of matrices A and B and then finding its determinant results in 100.
862 Easy
862 of 995
Analyzing +4 | -1
The system of simultaneous equations kx+2y−z=1  (k−1)y−2z=2kx + 2y - z = 1\;\left( {k - 1} \right)y - 2z = 2 and (k+2)z=3\left( {k + 2} \right)z = 3 has a unique solution, if kk equals
View answer and explanation
Correct option: B
−1- 1
Option B (-1) is correct because for a unique solution, the determinant of the coefficient matrix must be non-zero, leading to the condition k ≠ 0, 1, or -2.
863 Easy
863 of 995
Analyzing +4 | -1
The value of the determinant ∣10!11!12!11!12!13!12!13!14!∣,\left|\begin{array}{lll}10 ! & 11 ! & 12 ! \\ 11 ! & 12 ! & 13 ! \\ 12 ! & 13 ! & 14 !\end{array}\right|, is
View answer and explanation
Correct option: C
2 (10 !11 !12 !)
Option C (2 (10 !11 !12 !)) is correct because after factoring out common terms and simplifying, the determinant evaluates to 2 (10 !11 !12 !).
864 Easy
864 of 995
Application +4 | -1
If p,q,rp, q, r are 3 real numbers satisfying the matrix equation, [pqr][341323202]=[301][p q r]\left[\begin{array}{lll}3 & 4 & 1 \\ 3 & 2 & 3 \\ 2 & 0 & 2\end{array}\right]=\left[\begin{array}{lll}3 & 0 & 1\end{array}\right] then 2p+q−r2 p+q-r equals :
View answer and explanation
Correct option: A
-3
Option A (-3) is correct because solving the matrix equation results in p=1, q=-2, r=3, and 2p+q-r = -3.
865 Easy
865 of 995
Application +4 | -1
If AA is a square matrix such that A2−A+I=0A^2-A+I=0, then the inverse of AA is
View answer and explanation
Correct option: A
I−AI-A
Option A (I−AI-A) is correct because from A2−A+I=0A^2 - A + I = 0, we can derive A(I−A)=IA(I-A) = I, showing that I−AI-A is the inverse of A.
866 Easy
866 of 995
Application +4 | -1
If AA and BB are square matrices of order 3 such that ∣A∣=−1,∣B∣=3,|A|=-1,|B|=3, then ∣3AB∣|3 A B| equals
View answer and explanation
Correct option: A
−9-9
Option A (-9) is correct because |3AB| = 33 |A||B| = 27 * (-1) * 3 = -81. There is a typo in the explanation provided in the original answer. The correct answer is -81, not -9.
867 Easy
867 of 995
Analyzing +4 | -1
Let AA be a matrix of order 3×33 \times 3 and det⁡(A)=2.\det \left( A \right) = 2. Then det⁡(det⁡(A)  adj(5  adj(A3)))\det \left( {\det \left( A \right)\,\,adj\left( {5\,\,adj\left( {{A^3}} \right)} \right)} \right) is equal to _______.
View answer and explanation
Correct option: A
512×106512 \times {10^6}
Option A (512×106512 \times {10^6}) is correct because it is the result of applying determinant and adjoint properties to the given matrix A.
868 Medium
868 of 995
Application +4 | -1
The value of Δ=∣122232223242324252∣,\Delta = \left| {\begin{array}{cccccccccccccccccccc} {{1^2}}&{{2^2}}&{{3^2}}\\ {{2^2}}&{{3^2}}&{{4^2}}\\ {{3^2}}&{{4^2}}&{{5^2}} \end{array}} \right|, is
View answer and explanation
Correct option: B
−8- 8
Option B (-8) is correct because the determinant simplifies to -8 after applying column operations.
869 Easy
869 of 995
Understanding +4 | -1
If A=(cos⁡θ−sin⁡θsin⁡θcos⁡θ)A=\left(\begin{array}{cc}\cos \theta & -\sin \theta \\ \sin \theta & \cos \theta\end{array}\right), then
View answer and explanation
Correct option: A
AA is an orthogonal matrix
Option A (AA is an orthogonal matrix) is correct because AA′=A′A=IA A^{\prime} = A^{\prime} A = I, which is the condition for a matrix to be orthogonal.
870 Medium
870 of 995
Analyzing +4 | -1
Let x,y,z>1x, y, z>1 and A=[1log⁡xylog⁡xzlog⁡yx2log⁡yzlog⁡zxlog⁡zy3]A=\left[\begin{array}{ccc}1 & \log _{x} y & \log _{x} z \\ \log _{y} x & 2 & \log _{y} z \\ \log _{z} x & \log _{z} y & 3\end{array}\right]. Then ∣adj⁡(adj⁡A2)∣\left|\operatorname{adj}\left(\operatorname{adj} A^{2}\right)\right| is equal to
View answer and explanation
Correct option: C
282^{8}
Option C (282^{8}) is correct because we simplify the determinant of the matrix A, then use the properties of adjoints and determinants to find the final value.
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