## CBSE Class 6 Maths Chapter 5 Notes Understanding Elementary Shapes

### Understanding Elementary Shapes Class 6 Notes Conceptual Facts

1. The distance between the end points of a line segment is called its length.

2. The length of a line segment is measured by graduated ruler.

3. The length of two line segments is compared by the divider.

4. An angle is formed by two arms (rays) with the same initial point.

5. An angle is measured in ‘degrees’.

6. An angle is measured by ‘protractor’.

7. Measure of one complete angle is 360°.

8. Measure of straight angle is 180°.

9. Measure of right angle is 90°.

10. An angle-less than 90° is called acute angle.

11. An angle more than 90° but less than 180° is called obtuse angle.

12. An angle greater than straight angle is called ‘reflex’ angle.

13. Two lines are said to be perpendicular to each other if the angle between them is 90°.

14. Two lines are parallel if they do not intersect each other even on producing to any extent.

15. Types of triangle on the basis of sides:

- Scalene: all the three sides are unequal in length.
- Isosceles: any two sides are equal in length.
- Equilateral: all the three sides are equal in length.

16. Types of triangle on the basis of angles:

- Acute triangle: each angles is less than 90° (acute)
- Right angled triangle: one of the three angles is (90°)
- Obtuse angled triangle : one of the three angle is more than 90°.

17. Polygon is a closed figure bounded by a certain number of line segments:

- Triangle: bounded by 3 sides.
- Quadrilateral: bounded by 4 sides.
- Pentagon: bounded by 5 sides.
- Hexagon: bounded by 6 sides.
- Heptagon: bounded by 7 sides.
- Octagon: bounded by 8 sides.

18. Types of quadrilateral:

- Parallelogram: Pair of opposite sides are equal and parallel.
- Square: each angle is 90° and all sides are equal.
- Rectangle: each angle is 90° and opposite sides are equal.
- Rhombus: a parallelogram with all equal sides.
- Trapezium: a pair of opposite sides are parallel.
- 3-D shapes: faces, edges and vertices are the elements of 3-D figures.