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

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

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

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

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

Area of Rhombus b h Area = bh d1 d2 Area = ½ d 1 d 2

h1 h2 A B C D Area of a general Quadrilateral Area = ½ AC ( h 1 + h 2 ) B A C D 3cm 5cm 8cm Area = ½ x 8 x ( ) = 4 x 8 = 32 cm 2

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

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

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