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1.3 Surface Areas of Objects Made from Right Rectangular Prisms.

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1 1.3 Surface Areas of Objects Made from Right Rectangular Prisms

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

3 Method 1 Draw all 6 views and count all the squares. Top Left Side Bottom Right Side Front Back

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

5 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

6 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 = 4cm 2 So the surface area is 18 x 4cm 2 = 72cm 2

7 Determining the Surface Area of a Composite Object Made from Right Rectangular Prisms 50m 20m 30m 10m

8 50 m 30 m 20 m 30 m 20 m 30 m 20 m 6 Squares, each have side length 10m

9 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.

10 Assignment Time


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