Lesson 4: Surface Area of Prisms6.GR.4

I can…

I can find the surface area of rectangular and triangular prisms.

Key words

• Surface area — The total area of all the flat sides of a solid.
• Rectangular prism — A solid box shape with six flat rectangle sides.
• Triangular prism — A solid with two triangle ends and three flat rectangle sides.
• Face — One flat side of a solid shape.
• Net — A flat shape that folds up into a solid.
• Lateral face — The side faces of a solid, not the top or bottom.

Steps

1. My triangular prism has triangle bases (base 6, height 4), is 10 long, and the two slant sides are 5 each.
2. Each triangle base is ½ × 6 × 4 = 12, and there are 2 of them: 2 × 12 = 24.
3. Now the 3 rectangles: 6 × 10 = 60, 5 × 10 = 50, and 5 × 10 = 50, which add to 160.
4. I add the bases and the rectangles: 24 + 160 = 184.
5. So the surface area is 184 in². I counted 5 faces because it is a triangular prism.

Try it

A rectangular prism has l = 8 ft, w = 6 ft, h = 3 ft. What is the surface area?

Check your answer

180 ft²

SA = 2(8×6) + 2(8×3) + 2(6×3) = 96 + 48 + 36 = 180 ft². Surface area uses square units (ft²).

Sentence starter

I know ___ because ___.

Goal: I can explain my work using the words surface area, rectangular prism, triangular prism, and face.