Area of the triangle = (1/2)*base* height = (1/2)*3*6 = 9 sm² We have 4 triangles like this one , so area of 4 triangles = 9*4 = 36 cm². Area of the square = 3*3 = 9 cm²
Surface area here means area all triangles + area of the square =36 +9 = = 45 cm ²
