Question:

Given below are two statements: one is labelled as Assertion A and the other is labelled as Reason R
Assertion A : Let $A = \begin{bmatrix} 3 & 0 & -1 \\ 3 & 0 & -1 \\ 4 & 0 & 5 \end{bmatrix}$, then $\text{Nullity}(A) = 1, \text{Rank}(A) = 2$. Reason R : For a linear transformation $T: \mathbb{R}^n \to \mathbb{R}^n$, $\text{Rank}(T) + \text{Nullity}(T) \neq n$. In the light of the above statements, choose the correct answer from the options given below

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Rank-Nullity Theorem is an equality: $\text{Rank}(T) + \text{Nullity}(T) = n$. Any assertion claiming $\neq n$ is immediately false!
Updated On: Jul 30, 2026
  • Both A and R are true and R is the correct explanation of A
  • Both A and R are true but R is NOT the correct explanation of A
  • A is true but R is false
  • A is false but R is true
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The Correct Option is C

Solution and Explanation

Step 1: Concept
The Rank-Nullity Theorem states that for any linear transformation $T: V \to W$ where $V$ is finite-dimensional: \[ \text{Rank}(T) + \text{Nullity}(T) = \dim(V) \]

Step 2: Key Formulas and Approach

Find the rank of matrix $A$ using row reduction, then use the Rank-Nullity Theorem to calculate nullity. Compare with Assertion A and Reason R.

Step 3: Step-by-step Explanation


Evaluating Assertion A: Given $A = \begin{bmatrix} 3 & 0 & -1
3 & 0 & -1
4 & 0 & 5 \end{bmatrix}$. Apply $R_2 \to R_2 - R_1$: \[ \begin{bmatrix} 3 & 0 & -1 0 & 0 & 0 4 & 0 & 5 \end{bmatrix} \] The rows $[3, 0, -1]$ and $[4, 0, 5]$ are clearly linearly independent. Therefore, the number of non-zero rows in row-echelon form is $2$, so $\text{Rank}(A) = 2$. By Rank-Nullity theorem for $3 \times 3$ matrix ($n = 3$): \[ \text{Nullity}(A) = 3 - \text{Rank}(A) = 3 - 2 = 1 \] Hence, Assertion A is true.
Evaluating Reason R: Reason R states that $\text{Rank}(T) + \text{Nullity}(T) \neq n$. By the fundamental Rank-Nullity Theorem, $\text{Rank}(T) + \text{Nullity}(T) = n$ strictly. The claim that it is $\neq n$ contradicts the theorem. Hence, Reason R is false.

Step 4: Final Answer

Assertion A is true, but Reason R is false. Thus, Option (C) is correct.
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