Answer:
perimeter = 2*a = 2*54 mm = 108 mm
Step-by-step explanation:
For any geometrical figure, the perimeter is the sum of all his sides.
In a rectangle figure, have four sides, two of them equals: a (upper side), b (lateral side), so the perimeter will be:
perimeter = a+a+b+b = 2*(a+b)
A square is a particular case of rectangle figure, in which: a = b.
So, for a square:
perimeter = 2*(a+a) = 2*(2a) = 4*a
