Stuck? Start here. Read the steps, try the problem, then check your answer.
I can…
I can find the surface area of rectangular and triangular prisms.
Key words
Surface Area of Prisms — The total area of all bases and lateral faces of a prism. Formula: SA = 2B + lateral area.
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.
Congruent — Exactly the same size and shape.
Steps
My triangular prism has triangle bases (base 6 in., height 4 in.), is 10 in. long, and the two slant sides are 5 in. each.
Each triangle base is ½ × 6 × 4 = 12, and there are 2 of them: 2 × 12 = 24.
Now the 3 rectangles: 6 × 10 = 60, 5 × 10 = 50, and 5 × 10 = 50, which add to 160.
I add the bases and the rectangles: 24 + 160 = 184.
So the surface area is 184 in². I counted 5 faces because it is a triangular prism.
Try it
You are painting every outside face of a toy chest at home. It is l = 5 ft, w = 4 ft, h = 2 ft. How many square feet will you paint (its surface area)?
Check your answer
76 ft²
SA = 2(5×4) + 2(5×2) + 2(4×2) = 40 + 20 + 16 = 76 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.