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NDA 2025
Exam
NDA
Year
2025
Subject
Mathematics
Chapter
Determinants

NDA 2025 · Mathematics · Determinants

Consider the following statements: Statement-I: If X is an n × n...

Consider the following statements:
Statement-I: If XX is an n×nn \times n matrix, then det⁡(mX)=mndet⁡(X)\det(mX) = m^n \det(X), where mm is a scalar.
Statement-II: If YY is a matrix obtained from XX by multiplying any row or column by a scalar mm, then det⁡(Y)=mdet⁡(X)\det(Y) = m\det(X).
Which one of the following is correct in respect of the above statements?

Options

  1. ABoth Statement-I and Statement-II are correct and Statement-II explains Statement-I
  2. BBoth Statement-I and Statement-II are correct but Statement-II does not explain Statement-I
  3. CStatement-I is correct but Statement-II is not correct
  4. DStatement-I is not correct but Statement-II is correct

Correct answer

A. Both Statement-I and Statement-II are correct and Statement-II explains Statement-I

Step-by-step solution

Statement-I states that for an n×nn \times n matrix XX, det⁡(mX)=mndet⁡(X)\det(mX) = m^n \det(X). This is a standard property of determinants and is correct.

Statement-II states that if a single row or column of a matrix is multiplied by a scalar mm, the determinant of the resulting matrix is mm times the determinant of the original matrix. This is also a fundamental property of determinants and is correct.

Multiplying a matrix XX by a scalar mm is equivalent to multiplying each of its nn rows by mm. By applying the property given in Statement-II nn times (once for each row), we can factor out mm from each of the nn rows, yielding mndet⁡(X)m^n \det(X).

Thus, Statement-II provides the logical reasoning required to prove Statement-I. Both statements are correct, and Statement-II explains Statement-I.
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