Page 2 - Lesson Notes-2-Ch.13 SA and Volumes(Cylinder)

= ( 2 × ℎ)
= ℎ cubic unit
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(N.B: The amount of space occupied by a solid cylinder is called its volume.)

Example-1
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Find the curved surface area (in cm ) of a cylinder of diameter 14 cm and height
20 cm.
Solution.
Here, Diameter (d) = 14 cm Height (h)= 20 cm
14

Radius ( r) = = = 7 cm
2 2
22
2
Curved Surface Area (CSA)= 2 ℎ = 2× × 7 × 20 = 880
7

Example- 2
A closed cylindrical vessel with diameter of base 20 cm and height
80 cm is made up of a metal sheet. Find the area of sheet used.
Solution. Diameter of the base = 20 cm

Therefore, radius of the base =
= 10 cm
Total surface area of a cylinder = 2 r(r + h)

= 5657.14 cm
2
Therefore, the area of the metal sheet required to make the vessel =
5657.14 cm .
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Example-3
The radii of two right circular cylinders are in the ratio 2:3 and their heights are
in the ratio 5: 4. Calculate the ratio of their curved surface areas.
Solution:

Let the radius of the first cylinder be 2x
and the radius of the second cylinder be 3x
Let the height of the first cylinder be 5y
and the height of the second cylinder be 4y
Therefore, curved surface area of the first cylinder
C1 = 2 (2x)(5y)
and curved surface area of the second cylinder
C2 = 2 (3x)(4y).

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