Welcome to Class 9 Maths chapter 13 Surface Area and Volume notes.The topics in this page are Surface area,Volume,supplimentary angles, Surface Area and Volume of Cube,cuboid, Cylinder,cone,Sphere,Hemissphere along with examples, and questions and answers .This is according to CBSE and the NCERT textbook. If you like the study material, feel free to share the link as much as possible.
Plane figure are the figure which lies in a plane or to put it simply which we can draw on a piece of paper Example : Triangle ,circle,quadilateral etc
We have already studied about perimeter and area of the plane figure
Just a recall of them
Solid Figure
Solid figure does not lie in a single plane.They are three dimensional figure Example:Cube ,Cylinder, Sphere
Mensuration
It is branch of mathematics which is concerned about the measurement of length ,area and Volume of plane and Solid figure
Perimeter
The perimeter of plane figure is defined as the length of the boundary
It units is same as that of length i.e. m ,cm,km
1 Meter
10 Decimeter
100 centimeter
1 Decimeter
10 centimeter
100 millimeter
1 Km
10 Hectometer
100 Decameter
1 Decameter
10 meter
1000 centimeter
Surface Area or Area
The area of the plane figure is the surface enclosed by its boundary
It unit is square of length unit. i.e. m2 , km2
1 square Meter
100 square Decimeter
10000 square centimeter
1 square Decimeter
100 square centimeter
10000 square millimeter
1 Hectare
100 squareDecameter
10000 square meter
1 square myraimeter
100 square kilometer
108 squaremeter
Volume
1 cm3
1mL
1000 mm3
1 Litre
1000mL
1000 cm3
1 m3
106 cm3
1000 L
1 dm3
1000 cm3
1 L
Surface Area and Volume of Cube and Cuboid
Type
Measurement
Surface Area of Cuboid of Length L, Breadth B and Height H
$2( LB + BH + LH )$.
Lateral surface area of the cuboids
$2( L + B ) \times H$
Diagonal of the cuboids
$\sqrt {L^2+B^2+H^2}$
Volume of a cuboids
$L \times B \times H$
Length of all 12 edges of the cuboids
$4 \times (L+B+H)$.
Surface Area of Cube of side L
$6L^2$
Lateral surface area of the cube
$4L^2$
Diagonal of the cube
$L \sqrt {3}$
Volume of a cube
$L^3$
Surface Area and Volume of Right circular cylinder
Radius
The radius (r) of the circular base is called the radius of the cylinder
Height
The length of the axis of the cylinder is called the height (h) of the cylinder
Lateral Surface
The curved surface joining the two base of a right circular cylinder is called Lateral Surface.
Type
Measurement
Curved or lateral Surface Area of cylinder
$2 \pi rh$
Total surface area of cylinder
$2 \pi r (h+r)$
Volume of Cylinder
$ \pi r^2 h$
Surface Area and Volume of Right circular cone
Radius
The radius (r) of the circular base is called the radius of the cone
Height
The length of the line segment joining the vertex to the centre of base is called the height (h) of the cone.
Slant Height
The length of the segment joining the vertex to any point on the circular edge of the base is called the slant height (L) of the cone.
Lateral surface Area
The curved surface joining the base and uppermost point of a right circular cone is called Lateral Surface
Type
Measurement
Curved or lateral Surface Area of cone
$ \pi rL$
Total surface area of cone
$ \pi r (L+r)$
Volume of Cone
$ \frac {1}{3} \pi r^2 h$
Surface Area and Volume of sphere and hemisphere
Sphere
A sphere can also be considered as a solid obtained on rotating a circle About its diameter
Hemisphere
A plane through the centre of the sphere divides the sphere into two equal parts, each of which is called a hemisphere
radius
The radius of the circle by which it is formed
Spherical Shell
The difference of two solid concentric spheres is called a spherical shell
Lateral Surface Area for Sphere
Total surface area of the sphere
Lateral Surface area of Hemisphere
It is the curved surface area leaving the circular base
Type
Measurement
Surface area of Sphere
$4 \pi r^2$
Volume of Sphere
$ \frac {4}{3} \pi r^3$
Curved Surface area of hemisphere
$ 2 \pi r^2$
Total Surface area of hemisphere
$3 \pi r^2$
Volume of hemisphere
$ \frac {2}{3} \pi r^3$
Volume of the spherical shell whose outer and inner radii and ‘R’ and ‘r’ respectively
$ \frac {2}{3} \pi (R^3-r^3)$
How the Surface area and Volume are determined
Area of Circle
The circumference of a circle is $2 \pi r$. This is the definition of π (pi). Divide the circle into many triangular segments. The area of the triangles is 1/2 times the sum of their bases, 2πr (the circumference), times their height, r.
$A= \frac {1}{2} \times 2 \pi r \times r= \pi r^2$
Surface Area of cylinder
This can be imagined as unwrapping the surface into a rectangle.
Surface area of cone
This can be achieved by divide the surface of the cone into its triangles, or the surface of the cone into many thin triangles. The area of the triangles is 1/2 times the sum of their bases, p, times their height,
$A= \frac {1}{2} \times 2 \pi r \times s=\pi rs$
How to solve Surface Area and Volume Problem
(1) We have told explained the surface area and volume of various common sold shapes.
(2) Try to divide the given solid shape into known shapes if the solid figure is other than known shapes
(3) Find out the given quantities like radius,height
(4) Apply the formula from the above given tables and get the answer
(5) Make sure you use common units across the problem
Solved example
Question 1
A cylinder is 50 cm in diameter and 3.5 m in height
(a) Find the radius
(b) Find the Curved Surface area
(c) Total Surface area
(d) Volume Solution
Height of the cylindrical pillar =h=3.5 m
Diameter of the cylindrical pillar =d=50 cm
So Radius of the cylindrical pillar =r=50/2=25 cm =0.25 m
So Curved surface of the cylindrical pillar =$2 \pi \times r \times h=5.5$ m2
Total Surface area= $2 \pi r h + 2 \pi r^2 =5.89$ m2
Volume =$\pi r^2 h=.17$ m3
Question 2
A cubical box has each edge 10 cm and another cuboidal box is 12.5 cm long, 10 cm wide and 8 cm high.
(i) Which box has the greater lateral surface area and by how much?
(ii) Which box has the smaller total surface area and by how much? Solution:
(i) Dimension of Cube
Edge of cube (a) = 10 cm Dimension of Cuboidal
Length (l) of box = 12.5 cm
Breadth (b) of box = 10 cm
Height (h) of box = 8 cm
Lateral surface area of cubical box is given by 4(a)2
= 4(10 cm)2
= 400 cm2
Lateral surface area of cuboidal box is given by 2[lh + bh]
= [2(12.5 × 8 + 10 × 8)] cm2
= (2 × 180) cm2
= 360 cm2
It is apparent from the data, 400 > 360
The difference =Lateral surface area of cubical box − Lateral surface area of cuboidal box = 400 cm2 − 360 cm2 = 40 cm2
So Lateral surface area of cubical box is greater than Lateral surface area of cuboidal box by 40 cm2
(ii) Total surface area of cubical box = 6(a)2 = 6(10 cm)2 = 600 cm2
Total surface area of cuboidal box
= 2[lh + bh + lb]
= [2(12.5 × 8 + 10 × 8 + 12.5 × 10] cm2
= 610 cm2
It is apparent from the data, 610 > 600
Difference=Total surface area of cuboidal box − Total surface area of cubical box = 610 cm2 − 600 cm2 = 10 cm2
So Lateral surface area of cuboidal box is greater than Lateral surface area of cubical box by 10 cm2
Summary
Here is surface area and volume class 9 notes Summary
