ISRO2014-72

Question

The rank of the matrix $A=\begin{pmatrix} 1 & 2 & 1 & -1\\ 9& 5& 2& 2\\ 7& 1& 0 & 4 \end{pmatrix}$  is ______ .

• A. $0$
• B. $1$
• C. $2$
• D. $3$

Comments

Please ask proper question.I can able to get this.is it 3*4 matrix or 4*4 matrix?

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A is not a matrix, it is merely a list of twelve numbers.

In order to define A as a matrix, along with the list, you need to describe few more attributes of A 

1) The dimension of the matrix( like 1x12 or 2x6 or 3x4 or 4x3 or 6x2 or 12x1 ?)

2) Row major order or column major order (or any other): If the matrix is multidimensional(like 2x6 or 3x4 or 4x3 or 6x2), then you need to describe the method you are using for storing multi-dimensional arrays in your single-dimensional list. 

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3*4 matrix

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 Isha Gupta $\begin{pmatrix} 1 & 2 &1 \\ -1& 9 &5 \\ 2& 2&7 \\ 1 &0 & 4 \end{pmatrix}$ .check matrix. 

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i said 3 * 4 1 2 1 -1 9 5 2 2 7 1 0 4

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1 2 1 -1

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tell if any mistake there in matrix. i will edit and post answer.

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$\begin{pmatrix} 1 & 2 & 1 & -1\\ 9& 5& 2& 2\\ 7& 1& 0 & 4 \end{pmatrix}$ check it now.

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ccorrect

Answer 1

Rank of Matrix is 2.

That's 2.

Comments

https://www.youtube.com/watch?v=24Jin6qm05o

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@ cse7 .Check this lecture.

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are you sure that once you once you find  ROW ECHELON FORM no need to reduce further??

Answer 2

R3 + 2R1 and then R3-R2. We get last row as zero. Hence, rank is 2.