The perimeter of any figure is the sum of the outline sides of the figure
Examples:
The perimeter of the triangle whose side length 2, 3, 5 is
P = 2 + 3 + 5 = 10 units
The perimeter of the square whose side 3 is
P = 3 + 3 + 3 + 3 = 12 units
The perimeter of the rectangle whose dimensions 4, 6 is
P = 4 + 6 + 4 + 6 = 20 units
Then you can find the perimeter of any figure by adding the length of its outline sides