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In Geometry, an object having width, height and depth is referred to as a 3D solid object. A cylinder is a solid that has two parallel circular bases connected by a curved surface. The axis of a cylinder is the line joining the centres of its two bases.

Types of cylinders

Cylinders can be either right cylinders or oblique cylinders.

If the two bases are exactly over each other then the cylinder is called a right cylinder. In a right cylinder the axis is at right angles to the base of the cylinder.

If the two parallel bases are not exactly over each other then the cylinder is called an oblique cylinder. In an oblique cylinder the axis is not at right angles to the bases of the cylinder.

Volume of a Cylinder

The volume of a cylinder is defined as the number of cubic units that will exactly fill the cylinder.

If r is the radius of the circular base of the cylinder and h is the height of the cylinder, then the volume of the cylinder is given by the formula
Volume = π r2 h

The volume is expressed in cubic units.

Practice questions:
Question: Find the volume of a cylinder with radius equal to 7 cms and height equal to 4 cms.
Height of the cylinder h = 4 cms
π = 22 / 7
Volume of the cylinder     = 22/ 7 * 7 * 7 * 4
= 616 cubic cms
)

Question: Find the volume of a cylinder with radius equal to 1 cms and height equal to 21 cms.
( Answer:  66 cubic cms )

Area of the cylinder

The surface area of a cylinder is calculated as the sum of the surface area of the curved surface of the cylinder and the surface area of the 2 circular ends of the cylinder.

If r is the radius of the cylinder, and h is height of the cylinder, then the area of the cylinder is given by the formula = 2 π r h + 2 π r2

The area of the cylinder is measured in sq cms.

Practice questions:
Question: Find the surface area of a cylinder with radius equal to 7 cms and height equal to 14 cms.
Height of the cylinder s = 14 cms
Area of the cylinder     = 2 * 22/7 * 7 * 14 + 2 * 22/7 * 7 * 7
= 616 + 308
= 924 sq cms
)

Question: Find the surface area of a cylinder whose circular base has a diameter of 14 cms and its height is equal to 10 cms.
( Answer:     Diameter of the circular base = 14 cms
Radius of the cylinder r = 14/2 = 7 cms
Height of the cylinder = 10 cms
Area of the cylinder     = 2 * 22/7 * 7 * 10 + 2 * 22/7 * 7 * 7
= 440 + 308
= 748 sq cms
)