# Chapter7C1.surface area

Chapter7C.1. Surface area Michael Liu Grade 9 Definition：surface area ?A plane face is one which is flat. ?This means that the surface area is the same as the area of the net required to make the Definition：surface area ?What does it mean to you? ?The surface area of a threedimensional solid with plane faces is the sum of the areas of the faces. Example : Triangular prism ? The surface area of the following triangular prism. B'' B' B' A'' B C' The SA is same as the area of : Area of side 1 Area of side 2 Area of side 3 Vocabulary A rectangular prism always has 6 faces, or sides. ____ Top Back Side 2 Front Bottom Side 1 Height (H) Width (W) Length (L) 5 More About Faces wait.. 1 Vocabulary To help us see all six faces of a rectangular prism, mathematicians sometimes unfold the rectangular prism to see a drawing called a net. Top Side Side Front Side Top Front Bottom You can easily see all three pairs of faces in a net. Internet applet: 7 Back Net of a cube wait.. 1 Practice – Independent Example So, how do we find the surface area of this rectangular prism? Let’s try an example… Front Back Side 1 Side 2 Top Bottom Take a couple minutes to see how many faces you can find the area of. If you can, also try to find the total surface area. 3 cm 4 cm 2 cm 8 Scaffolding Practice – Guided Example Surface area of the rectangular prism Side 2 Top Side Front Side Remember: Bottom Back Back Front = 4 cm x 3 cm = 12 cm2 = 12 cm2 = 6 cm2 = 6 cm2 = 8