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Let A=[aij]3×2A = [a_{ij}]_{3×2} and B=[bij]3×4B = [b_{ij}]_{3×4} be two matrices. Then the order of the matrix (AT.B)T(A^T . B)^T is:

Solution

✅ Correct Option: 2

Given matrix AA has order 3×23×2 (3 rows and 2 columns) and matrix BB has order 3×43×4 (3 rows and 4 columns).

When a matrix is transposed, rows become columns and columns become rows. If a matrix is m×nm×n, its transpose is n×mn×m.

For matrix multiplication X⋅YX \cdot Y to be possible, the number of columns in XX must equal the number of rows in YY. The resulting matrix has order (rows of XX) × (columns of YY).


Since AA is 3×23×2, applying transpose:

ATA^T is 2×32×3


To multiply AT⋅BA^T \cdot B:

ATA^T is 2×32×3 and BB is 3×43×4

Columns in ATA^T = 3 and rows in BB = 3, so multiplication is possible.

AT⋅BA^T \cdot B is 2×42×4


Since AT⋅BA^T \cdot B is 2×42×4, applying transpose:

(AT⋅B)T(A^T \cdot B)^T is 4×24×2


Therefore, the order of (AT⋅B)T(A^T \cdot B)^T is 4×24×2.

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