Class 9 — Mathematics

Q1. A matrix with only one row is called:

✔ Correct: B — A matrix having a single row is a row matrix.

Q2. The order of a matrix with 2 rows and 3 columns is:

✔ Correct: B — Order is written as rows x columns = 2 x 3.

Q3. A square matrix whose diagonal elements are 1 and all others 0 is:

✔ Correct: B — That is the identity (unit) matrix I.

Q4. Two matrices can be added only if they have:

✔ Correct: B — Addition requires both matrices to be of the same order.

Q5. The transpose of a row matrix is a:

✔ Correct: B — Transpose interchanges rows and columns.

Q6. If A is 2x3 and B is 3x4, then AB has order:

✔ Correct: A — AB takes rows of A and columns of B: 2x4.

Q7. A matrix A is singular if its determinant is:

✔ Correct: C — A singular matrix has determinant zero and no inverse.

Q8. The additive identity for matrices is the:

✔ Correct: B — Adding the zero matrix leaves a matrix unchanged.

Q9. In matrix [[1,2],[3,4]], the element a21 is:

✔ Correct: C — a21 means row 2, column 1, which is 3.

Q10. Which matrix has all elements zero?

✔ Correct: C — The null (zero) matrix has every element equal to zero.