# Y8MA3G_Surface area of cubes and cuboids_19_01_2012

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Category: Education

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### Surface area of cubes and cuboids :

Surface area of cubes and cuboids Lesson objective: To be able: to understand and calculate the surface area of cubes and cuboids. [Level 5/6] Key words: cubes cuboids Starter: Find the area of the shapes : 2 cm 4 cm 3 cm

### Slide 2:

How many faces has a cube? 2 2 2 What’s the shape of each face? What is a cube??? What’s the area of the one face? So, the total surface area of the cube is Area of cube

### Slide 3:

Work individually

### Slide 4:

The top and the bottom face of cuboid have the same area. How much is the area of the top face? Area of cuboid How much is the area of the bottom face? 2 1 3 A cuboid has 6 faces.

### Slide 5:

A cuboid has 6 faces. The front and the back face of cuboid have the same area. How much is the area of the front face? How much is the area of the back face? 2 1 3 Area of cuboid

### Slide 6:

A cuboid has 6 faces. The right end and the left end face of cuboid have the same area. How much is the area of the right end face? How much is the area of the left end face? 2 1 3 Area of cuboid

### Slide 7:

Surface area of cuboid = S = Surface area of cuboid = 22 cm² . 2 x (1 x 2) Top and bottom Area of cuboid + 2 x (2 x 3) Front and back 3 1 2 + 2 x (1 x 3) Right and left end

### Slide 8:

Surface area of cuboid = S = Surface area of cuboid = 2wl + 2lh + 2wh . 2 x wl Top and bottom Area of cuboid + 2 x lh Front and back h w l + 2 x wh Right and left end.

### Slide 9:

Find the surface area of the cuboid. Front: 4x8 = 32cm² Work individually… So, back: 4x8 = 32cm² Top: 4x5 = 20 cm² So, bottom: 4x5 = 20cm² 8 cm 4 cm 5 cm Right end: 5x8 = 40cm² So, left end: 4x8 = 40cm² Surface area = 20 + 20 + 32 + 32+ 40 + 40 =4 = 40 + 64 + 80 = 184 cm²

### Slide 10:

Work in pairs… a 280 cm2 b 132 cm2 c 310 cm2 d 92 cm2

### Slide 11:

PLENARY... Uncle Mike found that the area of this cube is 4 cm. Explain why his answer is wrong. 2 cm