RS Aggarwal Class-8 Three Dimensional Solids ICSE Maths Goyal Brothers

RS Aggarwal Class-8 Three Dimensional Solids ICSE Maths Goyal Brothers Prakashan Solutions Chapter-18. We provide step by step Solutions of Exercise / lesson-18 Three Dimensional Solids  for ICSE Class-8  RS  Aggarwal Mathematics.

Our Solutions contain all type Questions of Exe-18 A, Exe-18 B, Exe-18 C, with Notes to develop skill and confidence. Visit official Website CISCE for detail information about ICSE Board Class-8 Mathematics.

RS Aggarwal Class-8 Three Dimensional Solids ICSE Maths Goyal Brothers Prakashan Solutions Chapter-18


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Notes on Three Dimensional Solids

Exe-18 A,

 Exe-18 B,

 Exe-18 C,


Notes on Three Dimensional Solids

Geometry is one of the practical sections of Mathematics which involves various shapes and sizes of different figures and their properties. Geometry can be divided into two types: plane and solid geometry. Plane geometry deals with flat shapes like lines, curves, polygons, etc., that can be drawn on a piece of paper. On the other hand, solid geometry involves objects of three-dimensional shapes such as cylinders, cubes, spheres, etc. Here we will discuss a few fundamental elements of solid geometry – the three-dimensional shapes.

What are Three-Dimensional Shapes?

Shapes which can be measured in 3 directions are called three-dimensional shapes. These shapes are also called solid shapes. Length, width, and height (or depth or thickness) are the three measurements of the three-dimensional shapes. They are a part of three-dimensional geometry. They are different from 2D shapes because they have thickness.

Solid Shapes in Maths

The three-dimensional objects having depth, width and height are called solid shapes. Let us consider a few shapes to learn about them. You can find many examples of solid shapes around you. The mobile, notebook or almost everything you can see around is a solid shape.

Surface Area and Volume of 3D shapes

The two distinct measures used for defining the 3D shapes are:

  • Surface Area
  • Volume

Surface Area is defined as the total area of the surface of the three-dimensional object.  It is denoted as “SA”. The surface area is measured in terms of square units. The three different classifications of surface area are defined below. They are:

  • Curved Surface Area (CSA) is the area of all the curved regions
  • Lateral Surface Area (LSA) is the area of all the curved regions and all the flat surfaces excluding base areas
  • Total Surface Area (TSA) is the area of all the surfaces including the base of a 3D object

Volume is defined as the total space occupied by the three-dimensional shape or solid object. The volume is denoted as “V”. It is measured in terms of cubic units

A cube is a solid or three-dimensional shape which has 6 square faces. The cube has the following properties.

  • All edges are equal
  • 8 vertices
  • 12 edges
  • 6 faces

The surface area and the volume of the cube are given below:

The Surface Area of a Cube = 6asquare units

The volume of a Cube = a cubic units

Cuboid

A cuboid also called a rectangular prism, where the faces of the cuboid are a rectangle in shape. All the angle measures are 90 degree

  • 8 vertices
  • 12 edges
  • 6 faces

The surface area and the volume of the cuboid are given below:

The Surface Area of a Cuboid = 2(lb+bh+lh) Square units

The volume of a Cuboid = lbh Cubic units

Cylinder

A cylinder is defined as the three-dimensional geometrical figure which has two circular bases connected by a curved surface. A cylinder has

  • No vertex
  • 2 edges
  • 2 flat faces – circles
  • 1 curved face

Cone

A cone is a three-dimensional object or solid, which as a circular base and has a single vertex. The cone is a geometrical figure that decreases smoothly from the circular flat base to the top point called the apex. A cone has

  • 1 vertex
  • 1 edge
  • 1 flat face – circle
  • 1 curved face

The surface area and the volume of the cone are given below:

The Surface Area of a Cone = πr(r +√(r2+h2) Square units
Curved surface area of a cone =πrl
Slant height of a cone = l = √(r2+h2)

The volume of a Cone = ⅓ πr2h Cubic units

Sphere

A sphere is a three-dimensional solid figure which is perfectly round in shapes and every point on its surface is equidistant from the point is called the centre. The fixed distance from the centre of the sphere is called a radius of the sphere. A sphere has

  • No vertex
  • No edges
  • 1 curved face

The surface area and the volume of the sphere are given below:

The Curved Surface Area of a Sphere = 2πr² Square units

The Total Surface Area of a Sphere = 4πr² Square units

The volume of a Sphere = 4/3(πr3) cubic units


Exe-18 (A), RS Aggarwal Class-8 Three Dimensional Solids ICSE Maths Goyal Brothers Prakashan Solutions

Question 1 :

Below are given in 3D solid and their deference view. Label the view shown as front view, side view and top view and tick the one which is the best 2D representation of the object shown

3d solids chapter 18 class 8_1

Answer :

(i) 

(a) Front view

(b) Side  view

(c) Top view

(ii) 

(a) Top view

(b) Front view

(c) Side  view

(iii) 

(a)  Front view

(b) Top view

(iv) 

(a) Side  view

(b) Top view

(c) Front view

Question 2 :

Complete the following table by filling the number of faces, the number of edges and the number of vertices  for the given solid :

Solid No. of Faces No. of Edges No. of Vertices
(i) Cuboid …………………….. …………………….. ……………………..
(ii) Tetrahedron …………………….. ……………………… ……………………..
(iii) Rectangular Pyramid …………………….. …………………….. ……………………..
(iv) Pentagonal  Pyramid …………………….. …………………….. ……………………..
(v) Hexagonal Pyramid …………………….. …………………….. ……………………..
(vi) Triangular Prism …………………….. …………………….. ……………………..
(vii) Pentagonal Prism …………………….. …………………….. ……………………..
(viii) Hexagonal
Prism
…………………….. …………………….. ……………………..

Answer :

Solid No. of Faces No. of Edges No. of Vertices
(i) Cuboid 6 12 8
(ii) Tetrahedron 4 6 4
(iii) Rectangular Pyramid 5 8 5
(iv) Pentagonal  Pyramid  6 10 6
(v) Hexagonal Pyramid 7 12 7
(vi) Triangular Prism 5 9 6
(vii) Pentagonal Prism 7 15 10
(viii) Hexagonal
Prism
8 18 12

Question 3 :

 Fill in the blanks:

(i) A Square prism may also be called ………………

(ii) A tetrahedron has …………………. triangular faces.

(iii) A pentagonal pyramid has …. ………… triangular faces.

(iv) The five lateral faces of a pentagonal prism are ………………

(v) Two adjacent faces of a solid meet in  a / an ……………..

(vi) Two adjacent edges of a solid meet in a/an ………………

(vii) The side view of any pyramid depicts a ……………….

Answer :

(i) A Square prism may also be called cuboid

(ii) A tetrahedron has 4 triangular faces .

(iii) A pentagonal pyramid has 5 triangular faces.

(iv) The five lateral faces of a pentagonal prism are rectangle.

(v) Two adjacent faces of a solid meet in  a / an edge.

(vi) Two adjacent edges of a solid meet in a/an vertex

(vii) The side view of any pyramid depicts a triangle.

Question 4 :

Which of the following solids has the highest number of vertices ?

(i) Cuboid

(ii) Triangular Prism

(iii) Triangular Pyramid

(iv) Square Pyramid

Answer :

(i) Cuboid

Question 5 :

In which of the following solids, all the lateral faces are not triangular?

(i) Triangular Prism

(ii) Triangular Pyramid

(iii) Square Pyramid

(iv) Pentagonal Pyramid

Answer :

(i) Triangular Prism

Question 6 :

In which of the following solids, none of the faces is triangular?

(i) Triangular Prism

(ii) Square Pyramid

(iii) Pentagonal Pyramid

(iv) Hexagonal Prism

Answer :

(iv) Hexagonal Prism

Question 7 :

Look at the following picture :

Look at the following picture :

Which of the option given below correctly represent the view of the above object as seen from the top ?

Which of the option given below correctly represent the view of the above object as seen from the top ?

Answer :

(ii)

3d class 8 ch 18

Question 8 :

Choose the correct top view of the following jointed figure from the option given below it :

Choose the correct top view of the following jointed figure from the option given below it :

3d solids chapter 18 class 8_6

Answer :

3d solids chapter 18 class 8_7

Question 9 :

Below are given three view of a 3d-jointed figure :

Below are given three view of a 3d-jointed figure :

Choose the correct corresponding figure :

3d solids chapter 18 class 8_9

Answer :

3d solids chapter 18 class 8_10

Question 10:

Draw the correct 2D-front view of the jointed figure shown below :

Draw the correct 2D-front view of the jointed figure shown below :

Answer :

3d solids chapter 18 class 8_12


RS Aggarwal Class-8 Three Dimensional Solids Exe-18 (B), ICSE Maths Goyal Brothers Prakashan Solutions

Question 1 :

Define Euler’s relation for 3-D figures.

Answer :

Euler’s relation = F – V + V = 2

where V= number of vertices

E = number of edge

and F = number of faces

Question 2 :

How many edge are there in a

(i) Cube

(ii) Triangular prism

(iii) tetrahedron

(iv) squire pyramid

Answer :

(i) Cube =12

(ii) Triangular prism = 9

(iii) tetrahedron =6

(iv) squire pyramid = 8

Question 3 :

How many faces are there in a

(i) cuboid

(ii) pentagonal prism

(iii) tetrahedron

(iv) hexagonal pyramid

Answer :

Faces of

(i) Cuboid are  = 6

(ii) Pentagonal prism are = 7 (5+ 2)

(iii) Tetrahedron are = 4

(iv) Hexagonal pyramid are = 7

Question 4 :

How many vertices are there in a

(i) cube

(ii) triangular pyramid

(ii) square prism

(iv) triangular prism

Answer :

Vertices of

(i) Cube are = 8

(ii) Triangular pyramid are = 4

(ii) Square prism are = 8

(iv) Triangular prism are = 6

Question 5 :

Verify Euler’s relation for each of the following:

(i) cuboid

(ii) a triangular prism

(iii) a square pyramid

(iv) a tetrahedron

Answer :

(i) Cuboid

F – E + V = 2

6 – 12 + 8 = 2

14 – 12 = 2

2 = 2

(ii) A triangular prism

F – E + V = 2

5 – 9 + 6 = 2

11 – 9 = 2

2 = 2

(ii) A square pyramid

F – E + V = 2

5 – 8 + 5 = 2

10 – 8 = 2

2 = 2

(iv) A tetrahedron

F – E + V = 2

4 – 6 + 4 = 2

8 – 6 = 2

2 = 2


RS Aggarwal Class-8 Exe-18 (C), Three Dimensional Solids ICSE Maths Goyal Brothers Prakashan Solutions

 

Question 1:

Which solid figure would each of the following nets make when folded along dotted lines ?

Which solid figure would each of the following nets make when folded along dotted lines ?

Answer :

(i) Cuboid

(ii) Triangular Prism

Question 2:

Which of these nets cannot be folded to form a cube ?

Which of these nets cannot be folded to form a cube ?

Answer :

Not be Folded to form a cube are (i), (iv), (vi), and (x)

Question 3:

Which  of the following four nets cannot be folded to form a square pyramid ?

Which of the following four nets cannot be folded to form a square pyramid ?

Answer :

The nets cannot be folded to form a square pyramid is 

3d solids chapter 18 class 8_16

Question 4:

Shown below is a cuboid on the square grid given below.

Draw a net for the cuboid on the square grid given below.

Each square is 1 cm x 1 cm.

3Shown below is a cuboid on the square grid given below.

Answer :

Draw a net for the cuboid on the square grid given below.

 

–: End of RS Aggarwal Class-8 Three Dimensional Solids Solutions :–

Return to- RS Aggarwal Solutions for ICSE Class-8 Goyal Brothers Prakashan


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