# Surface Area of a Cube

Lateral surface area or the surface area of a cube of a cube = 4(side)^{2} sq. units = 4a^{2} sq. units

Total surface area of a cube = 6 (side)^{2} sq. units= = 6a^{2} sq. units

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Find the surface area and total surface area of a cube in each of the following:

(i) 9cm (ii) 3cm

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Let the edge of the cube = a cm

The surface area = 4a^{2} cm^{2}

Total surface area = 6a^{2} cm^{2}

(i) a = 9cm

Hence surface area = 4a^{2 }= 324 cm^{2}Â Â Â Â

and total surface area = 6a^{2 }= 486 cm^{2}

(ii) a = 3cm

Hence surface area = 4a^{2 }= 36 cm^{2}Â Â Â Â

and total surface area = 6a^{2 }= 54 cm^{2}Â

Let the edge of the cube = a cm

The surface area = 4a^{2} cm^{2}

Total surface area = 6a^{2} cm^{2}

(i) a = 9cm

Hence surface area = 4a^{2 }= 324 cm^{2}Â Â Â Â

and total surface area = 6a^{2 }= 486 cm^{2}

(ii) a = 3cm

Hence surface area = 4a^{2 }= 36 cm^{2}Â Â Â Â

and total surface area = 6a^{2 }= 54 cm^{2}Â

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# Surface Area of a Cuboid

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ÂLateral surface area or the surface area of a cuboid = 2( l+ b) x h sq. units

Total surface area of a cuboid = 2(lb + bh + hl) sq. units

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Find the surface area of a cuboid in each of the following:

(i) length = 8 cm, breadth = 5 cm, and height = 4 cm

(ii) length = 12 cm, breadth = 8.5 cm, height = 5 cm

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(i) Total surface area of the cuboidÂ = 2(lb + bh + hl)Â

Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â = 2(8 Â´ 5 + 5 Â´ 4 + 4 Â´ 8)

Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â = 184 cm^{2}

(iii) Total surface area = 2(lb + bh + hl)

Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â = 2(12 Â´ 8.5 + 8.5 Â´ 5 + 5 Â´ 12)

Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â = 409 cm^{2}