Imagine that you have a rope which is 24 cm long.
If you make a perfect square from this rope (each side is 6 cm) then the area becomes 6 x 6 = 36 cm^2.
If you make a perfect triangle (each side is 8 cm) from the same rope, then the area becomes (768)^0.5 which is approx. 28 cm^2
So the length of your border is always the same, but this same border length surrounds different amount of area for different shapes.
The border length is the same, but the area size is different.
I am not asking mathematical explanation, but I am searching for the logical explanation. What is the logic behind this? Difficult to understand the logic.