Answer:
Geometrically, ca is an extension or contraction of a, and algebraically is a multiplication of c times every coordinate of a.
Step-by-step explanation:
<em>A vector is an element of a vectorial space which could have n-coordinates</em> (or dimensions). <em>A scalar is just a number</em> (they don't specify if it is real, complex, rational, etc.).
In order to find ca (or c*a), we have that, in general

is the vector a, and ca is c times the vector a

Geometrically, this <em>represents an extension or contraction of the vector a</em>.