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

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

4. 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

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

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

7. 2 (l +b) 4a 2π r Perimeter 2r π r π r + 2r

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

9. 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 ( 3 + 5 ) = 4 x 8 = 32 cm 2

10. 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

11. 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* ( 10 + 6 ) * 5 = 1/2 * ( 1 6 ) * 5 = 8 * 5 = 40 cm 2

12. 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