Question

If $Tr\left(A\right)=6,$ then $Tr\left(4A\right)=$

• A. $\frac{3}{2}$
• B. $2$
• C. $12$
• D. $24$

Answer 1

Answer: (D)

$24$

$Tr\left(A\right)$ is the sum of the diagonal elements of $A$.

Now, $4A$ gives each element of $A$ multiplied by $4$, then

$Tr\left(4A\right)$ $=4\times$ the sum of diagonal elements of $A$.

$\Rightarrow Tr\left(4A\right)=4Tr\left(A\right)=4\times 6=24$.