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Important Questions: CBSE Class 12 Mathematics Chapter 3 Matrices
Matrices is a scoring yet calculation-intensive chapter in CBSE Class 12 Mathematics. It bridges pure algebra with applications in computer science, economics, and engineering. CBSE frames questions that test both conceptual clarity — transpose rules, symmetric and skew-symmetric properties — and computational accuracy in addition, multiplication, and matrix equations. This question bank mirrors the latest board exam pattern, grouping problems by marks so you can practise strategically and identify your weak areas before the exam.
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Key takeaways
- ✓Chapter 3 Matrices typically carries 8-12 marks in the CBSE Class 12 board exam, spread across 1-mark MCQs to 5-mark case-study questions.
- ✓Master the transpose properties and symmetric/skew-symmetric decomposition — they appear in 2-mark and 3-mark sections almost every year.
- ✓1-mark MCQs test quick recall of order, element positions, and type of matrices; speed and accuracy matter.
- ✓3-mark questions often ask you to verify matrix equations like (AB)' = B'A' or express a matrix as sum of symmetric and skew-symmetric parts.
- ✓5-mark case-based questions integrate matrices with real-life contexts; read the case carefully and extract numerical data before solving.
- ✓Common errors include wrong order during multiplication, sign mistakes in transpose, and confusing rows with columns — double-check dimensions.
Chapter Overview and Marks Weightage in CBSE Exam
Chapter 3 Matrices in NCERT Class 12 Mathematics introduces matrix notation, order, types, and fundamental operations including addition, scalar multiplication, matrix multiplication, and transpose. CBSE typically allocates 8-12 marks to this chapter across the 80-mark theory paper. In recent years, the pattern has been one 1-mark MCQ, one 2-mark VSA, one 3-mark short-answer question, and one 5-mark case-based question. The case-study often integrates matrices with real-world scenarios such as cost matrices, network models, or cryptography basics. Mastering operations and transpose properties is non-negotiable because they form the foundation for Determinants and Adjoint chapters that follow. Focus on speed for MCQs and methodical working for long answers to maximise your score in this chapter during the board exam.
- Typical weightage: 8-12 marks in the CBSE Class 12 board paper
- Question types: 1-mark MCQ, 2-mark VSA, 3-mark numerical, 5-mark case-based
- Core topics: matrix order, types (row, column, square, diagonal, scalar, identity, zero), addition and multiplication, transpose properties, symmetric and skew-symmetric matrices
- Case-based questions integrate matrices with practical contexts like cost, network, or transformation matrices
1-Mark Questions (MCQ / Very Short Answer)
One-mark questions test instant recall and conceptual clarity. CBSE frames these as multiple-choice or fill-in-the-blank questions. You must answer within 30 seconds. Common themes include identifying matrix order, type of matrix, element positions, and basic properties of transpose and symmetric matrices. Practice these daily to ensure you do not drop easy marks on exam day. Below are six representative 1-mark questions with concise model answers to guide your revision and build confidence in rapid problem-solving under time pressure during the board examination.
- Q1. If A is a 3×4 matrix and B is a matrix such that A'B and BA' are both defined, what is the order of B? — Answer: B must be 3×3.
- Q2. A square matrix A is said to be symmetric if — Answer: A' = A.
- Q3. If A is a skew-symmetric matrix of order 3, what is the sum of its diagonal elements? — Answer: 0 (all diagonal elements of a skew-symmetric matrix are zero).
- Q4. For matrices A and B, (A + B)' equals — Answer: A' + B'.
- Q5. The number of all possible matrices of order 2×3 with each entry 0 or 1 is — Answer: 2^6 = 64.
- Q6. If A = [aᵢⱼ] is a square matrix of order 2 such that aᵢⱼ = i - j, then A is — Answer: skew-symmetric (since aᵢⱼ = -aⱼᵢ).
2-Mark Questions (Short Answer - I)
Two-mark questions require you to show working but remain concise. CBSE typically asks you to compute a specific element, verify a property, or find one matrix given conditions. These questions reward clarity and correct notation. Write the given matrix, state the operation, perform one or two calculation steps, and box your final answer. Avoid lengthy explanations; examiners award full marks for correct method and answer even if intermediate algebra is brief. Below are four carefully chosen 2-mark questions that mirror past board papers and cover transpose, symmetric matrices, and basic operations essential for scoring well in this segment of the examination.
- Q1. If A = [[2, -1], [3, 4]] and B = [[1, 2], [-1, 0]], find 2A - 3B. — Answer: 2A = [[4, -2], [6, 8]]; 3B = [[3, 6], [-3, 0]]; 2A - 3B = [[1, -8], [9, 8]].
- Q2. Find the transpose of the matrix A = [[1, 2, 3], [4, 5, 6]]. — Answer: A' = [[1, 4], [2, 5], [3, 6]].
- Q3. Show that the matrix A = [[0, 5], [-5, 0]] is skew-symmetric. — Answer: A' = [[0, -5], [5, 0]] = -A, hence skew-symmetric.
- Q4. If A = [[1, 2], [3, 4]] and B = [[2, 0], [1, 3]], verify that (A + B)' = A' + B'. — Answer: (A+B) = [[3, 2], [4, 7]]; (A+B)' = [[3, 4], [2, 7]]; A' = [[1, 3], [2, 4]], B' = [[2, 1], [0, 3]]; A'+B' = [[3, 4], [2, 7]]. Verified.
3-Mark Questions (Short Answer - II)
Three-mark questions demand multi-step working and involve matrix multiplication, verification of transpose laws, or expressing matrices as sums of symmetric and skew-symmetric parts. CBSE rewards partial marks for correct method even if the final answer has a minor arithmetic slip. Always write the formula or theorem you are applying, show at least two intermediate steps, and circle your final answer. These questions separate average students from toppers because they test both conceptual understanding and computational accuracy. Below are four representative 3-mark questions with detailed model answers that cover the breadth of topics in Matrices and align perfectly with the latest CBSE marking scheme and exam pattern for Class 12 Mathematics board examinations.
- Q1. If A = [[1, 2], [3, 4]] and B = [[2, 1], [1, 0]], find AB and verify that (AB)' = B'A'. — Answer: AB = [[4, 1], [10, 3]]; (AB)' = [[4, 10], [1, 3]]; B' = [[2, 1], [1, 0]], A' = [[1, 3], [2, 4]]; B'A' = [[4, 10], [1, 3]]. Verified.
- Q2. Express the matrix A = [[6, -2, 2], [-2, 3, -1], [2, -1, 3]] as the sum of a symmetric and a skew-symmetric matrix. — Answer: Symmetric part P = (A + A')/2 = [[6, -2, 2], [-2, 3, -1], [2, -1, 3]]; Skew-symmetric part Q = (A - A')/2 = [[0, 0, 0], [0, 0, 0], [0, 0, 0]] (A is already symmetric, Q is zero matrix).
- Q3. If A is a square matrix such that A² = A, show that (I + A)³ = I + 7A, where I is the identity matrix. — Answer: (I+A)³ = I + 3A + 3A² + A³ = I + 3A + 3A + A = I + 7A (using A² = A implies A³ = A).
- Q4. Find the matrix X if 2X + [[1, 2], [3, 4]] = [[5, 6], [7, 8]]. — Answer: 2X = [[4, 4], [4, 4]]; X = [[2, 2], [2, 2]].
5-Mark Questions (Long Answer / Case-Based)
Five-mark questions in recent CBSE papers are often case-based, presenting a real-world scenario followed by sub-questions. These questions test your ability to extract numerical information, set up matrix equations, and perform operations correctly. Even if the context is unfamiliar — cryptography, network models, cost analysis — the mathematics remains standard matrix operations and properties. Read the case twice, underline numerical data, write down matrices explicitly, and solve each sub-question methodically. CBSE awards step-wise marks, so even partial solutions earn credit. Below are three comprehensive 5-mark questions: two case-based and one traditional long-answer problem. Each includes a worked model answer to help you understand the level of detail and presentation expected on the board exam for full marks in this high-value section.
- Q1. Case-Based: A firm produces two products P and Q. The profit per unit of P is ₹50 and Q is ₹30. The firm operates two factories A and B. Factory A produces 40 units of P and 20 units of Q per day; factory B produces 30 units of P and 50 units of Q per day. (i) Represent production in a 2×2 matrix M. (ii) Represent profit per unit in a 2×1 matrix N. (iii) Find the daily profit from each factory using matrix multiplication. — Answer: (i) M = [[40, 20], [30, 50]] (rows: factories; columns: products). (ii) N = [[50], [30]]. (iii) MN = [[40×50 + 20×30], [30×50 + 50×30]] = [[2600], [3000]]. Factory A earns ₹2600, factory B earns ₹3000 daily.
- Q2. Case-Based: A coding system uses a 2×2 encoding matrix E = [[1, 2], [3, 5]]. A message is represented by the matrix C = [[7, 11], [16, 26]]. (i) Verify that E is invertible by finding its determinant. (ii) Decode the message by finding EC⁻¹ if C is obtained by multiplying E with the original message matrix M. — Answer: (i) det(E) = 1×5 - 2×3 = -1 ≠ 0, so invertible. (ii) Since C = EM, M = E⁻¹C. E⁻¹ = [[-5, 2], [3, -1]]. M = E⁻¹C = [[-5×7+2×16, -5×11+2×26], [3×7-1×16, 3×11-1×26]] = [[3, 7], [5, 7]]. Decoded message matrix is [[3, 7], [5, 7]].
- Q3. Long Answer: If A = [[3, -2, 3], [2, 1, -1], [4, -3, 2]], find A² and show that A² - 4A - 5I = O (zero matrix). Hence find A⁻¹. — Answer: Compute A² = [[17, -17, 17], [4, -2, 3], [14, -17, 17]]. Then A² - 4A - 5I = O (verify by substitution). Rearrange: A² = 4A + 5I. Multiply both sides by A⁻¹: A = 4I + 5A⁻¹, so A⁻¹ = (A - 4I)/5. Compute A - 4I = [[-1, -2, 3], [2, -3, -1], [4, -3, -2]]. Hence A⁻¹ = (1/5)[[-1, -2, 3], [2, -3, -1], [4, -3, -2]].
How CBSE Frames Questions from Matrices
CBSE question-setters follow a predictable blueprint for Matrices. One-mark MCQs test definitions and instant properties — order, transpose, symmetric/skew-symmetric identification. Two-mark questions ask you to perform one matrix operation or verify a single property numerically. Three-mark questions combine two operations, such as multiplication followed by transpose verification, or expressing a matrix as symmetric plus skew-symmetric. Five-mark case-based questions embed matrices in a story — production, cost, cryptography, network — and ask 3-4 sub-questions that build on each other. Examiners reward clear notation, correct arithmetic, and logical flow. Always label matrices, write intermediate steps, and underline or box final answers. Understanding this pattern helps you allocate revision time wisely and approach each question type with a clear strategy during the board examination.
- MCQs favour quick recall: order, type, diagonal sum, transpose properties
- 2-mark VSAs test single operations: addition, scalar multiplication, transpose, element extraction
- 3-mark questions combine operations: AB then (AB)', or decompose into symmetric + skew-symmetric
- 5-mark case-based questions present a real-world scenario with 3-4 sub-parts; read the case carefully and extract numerical data before solving
- Marks are awarded step-wise; partial credit for correct method even if final answer is wrong
- Common command words: 'Find', 'Verify', 'Express', 'Show that', 'Compute' — each implies a different level of working
Common Mistakes Students Make in Matrices
Even strong students lose marks in Matrices due to avoidable errors. The most frequent mistake is wrong order during multiplication — remember, AB is defined only if the number of columns in A equals the number of rows in B, and the result has order (rows of A) × (columns of B). Sign errors plague transpose and skew-symmetric problems; double-check minus signs when computing A - A'. Another pitfall is confusing rows with columns when writing elements; always write aᵢⱼ means i-th row, j-th column. Students also forget to verify both directions when proving properties like (AB)' = B'A' — compute both sides independently. In case-based questions, many jump to calculation without clearly defining matrices first. Finally, arithmetic slips in 3×3 multiplication cost marks; use rough work space and verify your answer by checking one row-column product. Awareness of these errors and deliberate practice will significantly improve your accuracy and confidence during the board exam.
- Wrong order during multiplication: always check (m×n)(n×p) = (m×p); mismatch means multiplication is undefined
- Sign errors in transpose and skew-symmetric: A' switches rows and columns; aᵢⱼ becomes aⱼᵢ, so watch minus signs
- Confusing row index with column index: aᵢⱼ is row i, column j; writing a₂₃ means second row, third column
- Incomplete verification: when asked to verify (AB)' = B'A', compute both (AB)' and B'A' independently and show they are equal
- Not defining matrices in case-based questions: before multiplying, write out the matrices with proper labels and dimensions
- Arithmetic slips in 3×3 multiplication: double-check each element; use rough work and verify at least one row-column product
Tips to Master Matrices for Board Exams
Start revision by memorising definitions and properties from NCERT: order, types, transpose laws, conditions for symmetric and skew-symmetric matrices. Then practice NCERT Examples and Exercise questions until you can solve them without referring to solutions. Move to CBSE sample papers and previous years' question papers, timing yourself strictly. For MCQs, aim to answer in 30 seconds; for 5-mark questions, allocate 8-10 minutes. Write every step even in practice; this habit prevents mistakes under exam pressure. Use graph paper or ruled sheets to keep matrices aligned — neat presentation earns goodwill marks. Revise the symmetric and skew-symmetric decomposition formula daily for one week before the exam; it appears almost every year in 2-mark or 3-mark questions. For case-based questions, practice converting word problems into matrices; underline numerical data and label rows and columns clearly. Finally, verify your answers by checking dimensions and one sample element. Consistent, focused practice for 30-45 minutes daily over four weeks will make Matrices one of your highest-scoring chapters in the CBSE Class 12 Mathematics board exam.
- Memorise NCERT definitions and transpose properties; write them on a flashcard for daily revision
- Solve all NCERT Examples and Exercises without looking at solutions; redo wrong questions immediately
- Practice CBSE sample papers and previous years' papers under timed conditions; track your speed and accuracy
- Write every step neatly; align matrices using ruled paper or graph paper to avoid row-column misalignment
- Revise the formula A = (A+A')/2 + (A-A')/2 daily; this decomposition question is a board exam favourite
- For case-based questions, first extract and label all numerical data as matrices before attempting sub-questions
- Verify final answers by checking order and computing one element independently to catch arithmetic errors
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How CBSETUTOR.ai Helps You Ace Matrices
Matrices questions can be tricky, especially when you are stuck on a multiplication step or unsure whether your decomposition into symmetric and skew-symmetric parts is correct. CBSETUTOR.ai gives you a 24×7 AI tutor that solves your doubts instantly. Snap a photo of any Matrices problem from your textbook or test paper, upload it, and receive step-by-step worked solutions with explanations tailored to CBSE marking schemes. Whether you are revising transpose properties at 11 PM or practising case-based questions on a Sunday morning, the AI tutor is always available. The platform covers every NCERT exercise, CBSE sample paper, and previous years' question from Class 6 to 12, all at a flat fee of ₹999 per month — one price for every class and subject. Start with a 3-day free trial, upload your toughest Matrices questions, and see how personalised, on-demand help accelerates your understanding and boosts your board exam score. Thousands of CBSE students across India trust CBSETUTOR.ai to fill gaps that classroom teaching and static video lectures leave behind, making it an essential tool for board exam preparation.
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- Personalised explanations adapt to your current level, helping you progress from basic operations to complex case-based questions
Frequently asked questions
How many marks does Chapter 3 Matrices carry in CBSE Class 12 board exam?+
Matrices typically carries 8-12 marks in the CBSE Class 12 Mathematics board exam. The distribution includes one 1-mark MCQ, one 2-mark VSA, one 3-mark short-answer question, and one 5-mark case-based question. Weightage may vary slightly year to year, but the chapter is consistently high-value.
What are the most important topics in Matrices for board exams?+
Focus on transpose properties (especially reversal laws for sum and product), symmetric and skew-symmetric matrices, and expressing a matrix as the sum of symmetric and skew-symmetric parts. Matrix multiplication and verification of identities like (AB)' = B'A' are also frequently tested.
How do I remember the formula for symmetric and skew-symmetric decomposition?+
Any square matrix A can be written as A = (A + A')/2 + (A - A')/2, where (A + A')/2 is symmetric and (A - A')/2 is skew-symmetric. Write this formula on a flashcard and revise daily. Practice 5-6 numerical examples to internalise the steps.
What is the most common mistake students make in matrix multiplication?+
Students often forget to check order compatibility. AB is defined only if the number of columns in A equals the number of rows in B. The resulting matrix has order (rows of A)×(columns of B). Always write dimensions before multiplying to avoid this error.
Are case-based questions on Matrices difficult?+
Case-based questions look lengthy but are straightforward if you extract numerical data carefully and set up matrices correctly. Read the case twice, underline numbers, label rows and columns, and solve sub-questions step-by-step. Practice 8-10 case-based questions from CBSE sample papers to build confidence.
How much time should I spend on a 5-mark Matrices question in the exam?+
Allocate 8-10 minutes for a 5-mark question. Spend 1-2 minutes reading and setting up matrices, 5-6 minutes solving, and 1-2 minutes verifying your answer. Practice under timed conditions at home to develop speed and accuracy.
Do I need to write every step in 2-mark questions?+
Yes. Even for 2-mark questions, show the operation, one or two intermediate steps, and the final answer. CBSE awards partial marks for correct method. Skipping steps risks losing marks if your final answer is wrong.
Can I score full marks in Matrices with just NCERT?+
NCERT is the foundation, and most board questions are NCERT-level or slight variations. Solve all NCERT Examples and Exercises thoroughly. Then practise CBSE sample papers and previous years' questions to familiarise yourself with question phrasing and case-based formats for complete exam readiness.
What is the difference between symmetric and skew-symmetric matrices?+
A square matrix A is symmetric if A' = A (transpose equals the matrix itself). A is skew-symmetric if A' = -A (transpose equals negative of the matrix). In skew-symmetric matrices, all diagonal elements are zero. These definitions are directly from NCERT and are tested in 1-mark and 2-mark questions.
How can CBSETUTOR.ai help me with Matrices doubts at odd hours?+
CBSETUTOR.ai offers a 24×7 AI tutor. Upload a photo of your Matrices question anytime — late night, early morning, or weekends — and receive instant step-by-step solutions. The platform is especially useful for clearing doubts when your school teacher or coaching tutor is unavailable. Try the 3-day free trial to experience on-demand doubt solving for yourself.
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