Matrices & Determinants
Q. Calculate the determinant of the matrix J = [[1, 2, 1], [0, 1, 0], [2, 3, 1]]. (2023)
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Solution
The determinant of J is calculated as 1*(1*1 - 0*3) - 2*(0*1 - 0*2) + 1*(0*3 - 1*2) = 1 - 0 - 2 = -1.
Correct Answer: B — 1
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Q. Find the eigenvalues of the matrix G = [[5, 4], [2, 3]]. (2020)
A.
1, 7
B.
2, 6
C.
3, 5
D.
4, 4
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Solution
The eigenvalues are found by solving the characteristic equation det(G - λI) = 0. This gives λ^2 - 8λ + 7 = 0, which factors to (λ - 1)(λ - 7) = 0, hence λ = 1, 7.
Correct Answer: A — 1, 7
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Q. If A is a 2x2 matrix and B is a 2x3 matrix, what is the order of the product AB? (2019)
A.
2x2
B.
2x3
C.
3x2
D.
2x5
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Solution
The order of the product of two matrices is determined by the outer dimensions. Here, A (2x2) and B (2x3) can be multiplied, resulting in a matrix of order 2x3.
Correct Answer: B — 2x3
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Q. If A is a 3x3 matrix, how many elements does it have? (2023)
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Solution
A 3x3 matrix has 3 rows and 3 columns, resulting in a total of 3 * 3 = 9 elements.
Correct Answer: B — 9
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Q. If a matrix is diagonal, what can be said about its non-diagonal elements? (2020)
A.
They are all zero
B.
They are all one
C.
They can be any value
D.
They are negative
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Solution
In a diagonal matrix, all non-diagonal elements are zero.
Correct Answer: A — They are all zero
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Q. If a square has a perimeter of 32 cm, what is the length of one side? (2023)
A.
8 cm
B.
10 cm
C.
12 cm
D.
6 cm
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Solution
The perimeter P of a square is given by P = 4 * side. If P = 32 cm, then side = 32/4 = 8 cm.
Correct Answer: A — 8 cm
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Q. If B = [[2, 3], [5, 7]], what is the value of det(B)? (2020)
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Solution
The determinant of B is calculated as (2*7) - (3*5) = 14 - 15 = -1.
Correct Answer: A — -1
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Q. If C = [[1, 0, 2], [0, 1, 3], [0, 0, 1]], what is det(C)? (2019)
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Solution
The determinant of an upper triangular matrix is the product of its diagonal elements. Here, det(C) = 1 * 1 * 1 = 1.
Correct Answer: B — 1
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Q. If D = [[4, 2], [1, 3]], find the inverse of D. (2022)
A.
[[3, -2], [-1, 4]]
B.
[[3, 2], [-1, 4]]
C.
[[3, -2], [1, 4]]
D.
[[4, -2], [-1, 3]]
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Solution
The inverse of D is given by (1/det(D)) * adj(D). Here, det(D) = (4*3) - (2*1) = 10, and adj(D) = [[3, -2], [-1, 4]]. Thus, D^(-1) = (1/10) * [[3, -2], [-1, 4]].
Correct Answer: A — [[3, -2], [-1, 4]]
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Q. If F = [[1, 2], [2, 4]], what is the determinant of F? (2021)
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Solution
The determinant of F is calculated as (1*4) - (2*2) = 4 - 4 = 0.
Correct Answer: A — 0
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Q. If I = [[1, 1], [1, 1]], what is the rank of I? (2022)
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Solution
The rank of I is 1 because all rows are linearly dependent.
Correct Answer: B — 1
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Q. If the lengths of the sides of a triangle are 3 cm, 4 cm, and 5 cm, what type of triangle is it? (2023)
A.
Acute
B.
Obtuse
C.
Right
D.
Equilateral
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Solution
A triangle with sides 3 cm, 4 cm, and 5 cm satisfies the Pythagorean theorem (3² + 4² = 5²), thus it is a right triangle.
Correct Answer: C — Right
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Q. If the radius of a circle is doubled, what happens to its area? (2020)
A.
It remains the same
B.
It doubles
C.
It triples
D.
It quadruples
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Solution
The area of a circle is given by A = πr². If the radius is doubled (r becomes 2r), the new area is A' = π(2r)² = 4πr², which is four times the original area.
Correct Answer: D — It quadruples
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Q. In a parallelogram, if one angle is 70 degrees, what is the measure of the opposite angle? (2019)
A.
70 degrees
B.
110 degrees
C.
90 degrees
D.
80 degrees
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Solution
In a parallelogram, opposite angles are equal. Therefore, if one angle is 70 degrees, the opposite angle is also 70 degrees.
Correct Answer: A — 70 degrees
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Q. In a right triangle, if one angle is 30 degrees, what is the ratio of the lengths of the sides opposite to the 30 degrees and 60 degrees angles? (2019)
A.
1:√3
B.
1:2
C.
√3:1
D.
2:1
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Solution
In a 30-60-90 triangle, the sides opposite the 30 degrees and 60 degrees angles are in the ratio 1:√3.
Correct Answer: A — 1:√3
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Q. What is the area of a triangle with a base of 8 cm and a height of 5 cm? (2020)
A.
20 cm²
B.
30 cm²
C.
40 cm²
D.
10 cm²
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Solution
The area of a triangle is given by A = 1/2 * base * height. Here, A = 1/2 * 8 * 5 = 20 cm².
Correct Answer: A — 20 cm²
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Q. What is the determinant of a 2x2 matrix A = [[a, b], [c, d]]? (2021)
A.
ad - bc
B.
ab + cd
C.
ac + bd
D.
ad + bc
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Solution
The determinant of a 2x2 matrix is calculated as ad - bc.
Correct Answer: A — ad - bc
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Q. What is the length of the diagonal of a rectangle with length 6 cm and width 8 cm? (2022)
A.
10 cm
B.
12 cm
C.
14 cm
D.
16 cm
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Solution
The length of the diagonal d of a rectangle can be found using the Pythagorean theorem: d = √(length² + width²) = √(6² + 8²) = √(36 + 64) = √100 = 10 cm.
Correct Answer: A — 10 cm
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Q. What is the order of a matrix with 3 rows and 4 columns? (2021)
A.
3x4
B.
4x3
C.
3x3
D.
4x4
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Solution
The order of a matrix is given by the number of rows followed by the number of columns. Therefore, a matrix with 3 rows and 4 columns is of order 3x4.
Correct Answer: A — 3x4
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Q. What is the perimeter of a rectangle with length 10 cm and width 5 cm? (2021)
A.
30 cm
B.
25 cm
C.
20 cm
D.
15 cm
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Solution
The perimeter of a rectangle is given by P = 2(length + width). Here, P = 2(10 + 5) = 30 cm.
Correct Answer: B — 25 cm
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Q. What is the rank of the matrix E = [[1, 2, 3], [4, 5, 6], [7, 8, 9]]? (2023)
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Solution
The rank of E is 2 because the rows are linearly dependent (the third row is a linear combination of the first two).
Correct Answer: B — 2
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Q. What is the trace of a square matrix? (2022)
A.
Sum of all elements
B.
Product of diagonal elements
C.
Sum of diagonal elements
D.
Difference of diagonal elements
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Solution
The trace of a square matrix is defined as the sum of the elements on its main diagonal.
Correct Answer: C — Sum of diagonal elements
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Q. What is the trace of the matrix H = [[2, 0, 1], [0, 3, 0], [1, 0, 4]]? (2019)
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Solution
The trace of a matrix is the sum of its diagonal elements. Here, trace(H) = 2 + 3 + 4 = 9.
Correct Answer: C — 7
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Q. What type of matrix has all its elements equal to zero? (2022)
A.
Identity matrix
B.
Zero matrix
C.
Diagonal matrix
D.
Scalar matrix
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Solution
A matrix where all elements are zero is called a zero matrix.
Correct Answer: B — Zero matrix
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Q. Which of the following is a square matrix? (2020)
A.
2x3
B.
3x3
C.
4x2
D.
5x1
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Solution
A square matrix is one where the number of rows is equal to the number of columns. Among the options, only 3x3 has equal rows and columns.
Correct Answer: B — 3x3
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Q. Which of the following is an identity matrix? (2019)
A.
[[1, 0], [0, 1]]
B.
[[1, 1], [1, 1]]
C.
[[0, 1], [1, 0]]
D.
[[2, 0], [0, 2]]
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Solution
An identity matrix is a square matrix with ones on the diagonal and zeros elsewhere. The matrix [[1, 0], [0, 1]] fits this definition.
Correct Answer: A — [[1, 0], [0, 1]]
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Q. Which of the following matrices is symmetric? (2023)
A.
A = [[1, 2], [3, 4]]
B.
B = [[1, 2], [2, 1]]
C.
C = [[1, 0], [0, 1]]
D.
D = [[1, 2, 3], [4, 5, 6]]
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Solution
A symmetric matrix is one that is equal to its transpose. Matrix B is symmetric because B = B^T.
Correct Answer: B — B = [[1, 2], [2, 1]]
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