To find the total surface area of the triangular prism, we need to calculate the lateral surface area and the two triangular base areas.
The lateral surface area of a triangular prism is given by the formula:
Lateral surface area = perimeter of base x height of prism
The perimeter of the base of the triangular prism is the sum of the three sides of the base triangle:
Perimeter of base = 12 + 12 + 18 = 42 cm
So, the lateral surface area of the triangular prism is:
Lateral surface area = 42 cm x 4 cm = 168 cm²
The area of each triangular base can be found using the formula:
Area of triangle = 1/2 x base x height
Therefore, the area of each triangular base is:
Area of triangle = 1/2 x 12 cm x 4 cm = 24 cm²
Now, we can find the total surface area of the triangular prism by adding the lateral surface area and the two triangular base areas:
Total surface area = Lateral surface area + 2 x Area of triangle
Total surface area = 168 cm² + 2 x 24 cm²
Total surface area = 168 cm² + 48 cm²
Total surface area = 216 cm²
Therefore, the total surface area of the triangular prism is 216 cm².