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MathsHardNumerical2021 ยท 24 Feb Shift 1

Q85.Let ๐‘€ be any 3 ร— 3 matrix with entries from the set 0, 1, 2. The maximum number of such matrices, for which the sum of diagonal elements of ๐‘€๐‘‡๐‘€ is seven, is______.

What This Question Tests

This question tests the understanding of matrix transpose and multiplication to derive the sum of diagonal elements, which simplifies to the sum of squares of all matrix entries. It then requires combinatorial analysis to count possible matrices whose entries (from {0,1,2}) sum up to 7 when squared.

Concepts Tested

Matrix multiplicationTranspose of a matrixTrace of a matrixCounting principles

Formulas Used

(M^T M)_{ii} = \sum_{k=1}^{3} (M_{ki})^2

Trace(M^T M) = \sum_{i=1}^{3} \sum_{k=1}^{3} (M_{ki})^2

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๐Ÿ“‹ Question Details

Chapter
Matrices
Topic
Matrix multiplication and properties
Year
2021
Shift
24 Feb Shift 1
Q Number
Q85
Type
Numerical
NCERT Ref
Class 12 Mathematics Ch 3: Matrices

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