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3 and 4 .Determinants and Matrices
medium
$A$ and $B$ are two given matrices such that the order of $A$ is $3×4$ , if $A’ B$ and $BA’$ are both defined then
A
order of $B’$ is $3 × 4$
B
order of $B’A$ is $4 × 4$
C
order of $B’A$ is $3 × 3$
D
$B’A$ is undefined
Solution
$A = 3 × 4 ; A’ = 4×3$
As $A’ B$ is defined ==> let order of $B = 3 × n$
now $BA’ = (3 ×n) × (4 × 3) ==> n = 4$
$\therefore$ order of $B is 3 × 4$
$\therefore$ order of $B’ = 4 × 3$
order of $B’ A = (4×3) × (3 × 4) = 4 × 4$
Standard 12
Mathematics