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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**