Page 8 - Lesson Notes-Ch.13 SA and Volumes(Cuboids and Cubes)

= 2(160 + 240 + 600)

= 2(1000) = 2000 cm
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Example- 2:

Find the total surface area of cuboid with dimensions 2 cm × 3 cm × 7
cm.
Solution: Given,
Length = 2 cm Breadth = 3 cm Height = 7 cm
Total Surface Area (TSA) = 2 (lb + bh + hl )
TSA = 2 ( 2×3 + 3×7 + 7×2)
TSA = 2 ( 6 + 21 + 14 )
TSA = 82
So, the total surface area of this cuboid is 82
2
Example -3:
The length, width and height of a cuboid are 12 cm, 13 cm and 15 cm
respectively. Find the lateral surface area of a cuboid.

Solution: Lateral surface area of a cuboid is given by:
LSA = 2h ( l + b )

LSA = 2×15 ( 12 + 13 )

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LSA = 750 c
Example- 4:

Find the surface area of a cube having its sides equal to 8 cm in
length.
Solution: Given length, ‘ ’= 8 cm

2
Surface area = 6
2
= 6× (8) = 6 ×64
= 384
2
Example -5:

Mary wants to decorate her Christmas tree. She wants to place the
tree on a wooden box covered with coloured paper with picture of
Santa Claus on it. She must know the exact quantity of paper to buy
for this purpose. If the length, breadth and height of a cuboidal box are
80 cm, 40 cm and 20 cm respectively. How many square sheets of
paper of side 40 cm would she require?
Solution

Given, Length = 80 cm Breadth = 40 cm Height = 20 cm

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