The perimeter of a closed figure is the length of its boundary.
Perimeter = Sum of all the sides.
= 1 cm + 4 cm + 0.5 cm + 2.5 cm + 2.5 cm + 0.5 cm + 4 cm = 15 cm.
Three sides of a triangle are of lengths 12.4 centimetres, 8.3 centimetres and 15.9 centimetres. Find the perimeter.