The figure below is formed by 3 big identical equilateral triangles and 3 small identical equilateral triangles. The length of GH is 54 cm. What is the perimeter of the figure?

1. Relate the bases of the triangles to the length of GH

The sum of the bases of the 6 equilateral triangles is equal to the length of $GH$, which is $54$ cm.

2. Relate the perimeter of the figure to the bases

Each equilateral triangle has $3$ equal sides. One side lies on $GH$, and the other $2$ sides contribute to the perimeter of the figure. Thus, the perimeter of the figure is $2$ times the sum of the bases.

3. Calculate the perimeter

$\text{Perimeter} = 2 \times 54 = 108 \text{ cm}$