$ \vec{A}=6\hat{i}+8\hat{j} $$ \vec{B}=210\hat{i}+280\hat{k} $$ \vec{C}=5.1\hat{i}+6.8\hat{j}=\frac{1}{20}(6\hat{i}+8\hat{j}) $$ \vec{D}=3.6\hat{i}+8\hat{j}+4.8\hat{k} $ Hence, it is clear that $ \text{\vec{A}} $ and $ \vec{C} $ are parallel and we can write as $ \vec{A}=\frac{1}{20}\vec{C} $ This implies that $ \text{\vec{A}} $ is parallel to $ \vec{C} $ and magnitude of $ \text{\vec{A}} $ is $ \frac{1}{20}. $
Vector Quantity is a physical quantity that is specified not only by its magnitude but also by its direction. A vector quantity whose magnitude is equal to one and has direction is called a unit vector.