1. Need for standard units.
2. Formulae for some geometrical figures.
3. Applications .

LINE SEGMENT
1 UNIT
How do we measure it?
The standard unit of length is meter.
The smaller units are mm, cm, dm.

REGION ENCLOSED BY
PLANE FIGURES
Which of the following encloses more region?
The amount of region enclosed by any plane figure is called its AREA

Its area is 1 cm 2
So area is measured in square units

l x b
Let us recall a 2 bh
π r 2
½ bh
½ π r 2

2 (l +b)
Perimeter
2 π r
π r
2r
4a
π r + 2r

h b
Area of Rhombus
Area = bh
Area = ½ d
1 d
2

A
D
Area of a general Quadrilateral
D
C
A
B
Area = ½ x 8 x ( 3 + 5 )
= 4 x 8
= 32 cm 2
B
C
Area = ½ AC ( h
1
+ h
2
)

TRAPEZIUM
A quadrilateral with one pair of opposite sides parallel
How to find the area of a trapezium ?
b lengths of parallel sides -a & b
Distance between parallel sides - h h a
Area of trapezium =
1/2 * ( Sum of parallel sides ) *Distance between them
Area = ½ * ( a + b ) * h

Find the area of the given trapezium.
10 cm a = 10 cm , b = 6 cm , h = 5 cm
5 cm
Area = ½ * ( a + b ) * h
6 cm
= 1 /2* ( 10 + 6 ) * 5
= 1/2 * ( 1 6 ) * 5
= 8 * 5
= 40 cm 2

ASSIGNMENT
Calculate the area of the given trapezium
ABCD in which AB // CD , AB = 16cm ,
CD = 12cm and the distance between
AB & CD is 15cm
D C
A
B