Surface Areas & VolumesSurface Areas & Volumes - Complete Collection
Class 9 Maths: Surface Areas & Volumes - Complete Collection
Area is the amount of space inside a boundary of a 2D object.
Surface area of a solid 3D object is the measure of the total area that a surface of an object occupies. It is measured in m2, cm2 etc
We generally talk about inner surface area & outer surface area.
Surface area is typically used to determine cost of painting for a given 3D object.
Volume is the quantity of 3D space enclosed by some closed boundary. It is measured in m3, cm3, ltr etc.
It is typically used to determine quantity of liquid, air, grains etc in a 3D container.
We will study Surface Area & Volume for Cube, Cuboid, Sphere, Cone and Cylinder.
Let’s define these terms
- Cuboid: Box shaped 3D solid object with 6 flat sides. All angles are right angles & all faces are rectangle.
- Cube: Box shaped 3D solid objects with 6 flat side. All angles are right angles & all faces are square. All sides are equal.
- Sphere: Perfectly round geometrical & circular 3D object like a ball. It is set of all points that are all at same distance from a given point (center) in a 3D space.
- Hemisphere: It is half of sphere.
- Cylinder: 3D surface formed by the points at a fixed distance from a given line segment called Axis. Solid enclosed by this surface & 2 planes perpendicular to axis is called cylinder.
- Right Circular Cylinder: Cylinder where 2 planes are circular & also these planes are perpendicular to axis.
- Cone: 3D object that tapers smoothly from a flat base to a point called apex or vertex. Base need not be circular
- Right Circular Cone: Cone with circular base & also base perpendicular to axis.
It has huge application in day to day life.
- Surface Area is used to find cost of painting a wall
- Volume is Used to find cost of building a wall
- Surface Area is used find cost of creating a box
- Volume is used to find the weight of grains that a box can hold
- Volume can also be used to find number of people that can stand in a room
- Surface area concept is required to find the cloth required to build a tent
- Surface area concept is also used to find cost of making pencil stand
- Volume Concept can be used to find number of pencils that a pencil stand can hold
- Volume concept can also be used to find the volume of water in a tank or well
2D sheets can be piled together to form 3D Cuboid
2D circular plates can be piled to form 3D Cylinder
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