1.3 Surface Areas of Objects Made from Right Rectangular Prisms

Determining the SA of a Composite Object Made From Cubes Each cube has edge length of 2cm. Determine the surface area.

Method 1 Draw all 6 views and count all the squares. Front Left Side Top 4 3 2 Bottom Right Side 3 Back 2 4 Total: 18 Squares

The area of each square is: A= l x w A= 2cm x 2cm = 4 cm2 We have 18 of these squares, so: Total Area = 18 x 4 cm2 = 72 cm2

Method 2 Our composite object is made up of 4 squares. Each cube has 6 square faces. So the total number of squares is: 4 x 6 = 18

The cubes overlap at 3 places, so there are 3x2, or 6 squares that are not included in the surface area. So the surface area in squares is: 24 – 6 = 18 Each square has area 2cm x 2cm = 4cm2 So the surface area is 18 x 4cm2 = 72cm2

Determining the Surface Area of a Composite Object Made from Right Rectangular Prisms

2 1 3 1 2 3 50 m 30 m 30 m 20 m 20 m 30 m 20 m 6 Squares, each have side length 10m

My favourite method: Figure out the Surface area of all the objects. Figure out the surface area where the objects overlap. Subtract that area from the total.

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