NAME-UDHAV ANAND

CLASS-VIIITH B

SUBMITTED TO-ANJALI MAM

The faces which bound a solid are called its surfaces and its area is called surface area.

The amount of space occupied by the bounding surface of a solid is called volume

A cube is a region of space formed by six identical square faces joined along their edges. Three edges join at each corner to form a vertex. The cube can also be called a regular hexahedron.

A cube is a three dimensional shape that features all right angles and a height, width and depth that are all equal.

Things that are shaped like a cube are often referred to as ‘cubic’.

A cube has the largest volume of all cuboids with a certain surface area.

11 different ‘nets’ can be made by folding out the 6 square faces of a cube.

EXAMPLE

Q. Find the volume of a cube of side 5 cm.

VOLUME=A3

=5*5*5 =125

A solid bounded by six rectangular plain is called a cuboide.g.book,matchbox

It has six flat sides and all angles are right angles

It is also a prism because it has the same cross-section along a length. In fact it is a rectangular prism

A cuboid has 6 faces A cuboid has 8 points (vertices).   A cuboid has 12 edges.

EXAMPLEQ. Find the volume of a brick 10 cm by 5

cm by 4 cm.

Volume=l*b*h

=10*5*4

=200

• A cone is a three dimensional object with a circular base that narrows toward a point, it looks similar to an ice cream cone.

• E.g.ice-cream cone

• The height of the cone is always perpendicular to the base

• A circular cone has a circular base, which is connected by a curved surface to its vertex. A cone is called a right circular cone, if the line from the vertex of the cone to the center of its base is perpendicular to the base.

EXAMPLE

Q. Find the volume of a cone whose height is 28 cm and radius of base is 21 cm

volume-(1/3)πr2h = (1/3) *(22/7)*21*21*28cm3

=12936cm3

A sphere is a solid with all its points the same distance from the center.

e.g.ball,earth,bubbles,orange

• A sphere is a perfectly round three dimensional shape similar to a round ball you might play sport with.

• All points on the surface of a sphere are the same distance from the center.

• A sphere is perfectly symmetrical around its center.

EXAMPLE

Q.Find the volume of sphere whose radius is 42 cm.

Radius=42 cm volume=(4/3)πr3 = (4/3) *(22/7)*42*42*42 =15212736

A cylinder is a solid with two congruent circles joined by a curved surface

e.g.pencil stand,roal rooler

• A cylinder is a three dimensional object with a circular base and straight parallel sides that looks similar to a can of coke.

• It has a flat base and a flat top • Because it has a curved surface it is

not a polyhedron

EXAMPLE

Q. Find the volume of the following cylinder:

radius-12cm height-24cm volume-πr2h =π*122*24 =10857.34

S.NO.

NAME OF SOLID T.S.A. C.S.A. VOLUME

1 CUBOID 2(lb+bh+lh) 2(l+b)h lbh

2 CUBE 6a2 4a2 a3

3 CYLINDER 2 πr(h+r) 2πrh πr2h

4 CONE πr(l+r) πrl (1/3)πr2h

5 SPHERE 4πr2 2πr2 (4/3)πr3