Here we can clearly say that AB > CD but sometimes it is difficult to tell which one is greater.
But this is a difficult method because every time to measure the different size of line segments we have to make a separate line segment.
Put the zero mark at point A and then move toward l to measure the length of the line segment, but it may have some errors on the basis of the thickness of the ruler.
This could be made accurate by using a Divider.
(i) Put the one end of the divider on point A and open it to put another end on point B.
(ii) Now pick up the divider without disturbing the opening and place it on the ruler so that one end lies on “0”.
(iii) Read the marking on the other end and we can compare the two line.
Angles
When two rays originate from a common point, then the turn between two rays around the common point or vertex is called the angle between the two rays.
Arms: The two rays joining to form an angle are called arms of an angle.
Vertex: The point at which two rays meet to form an angle is called the vertex of the angle.
There are four directionsNorth, South, East and West.
There are so many other types of angles which are not right or straight angles.
Example: What type of angle will be formed between the hour hand and the minute hand of a clock at 12:40?
Sol: Since the angle formed between the hour hand and the minute hand of a clock at 12:40 is greater than a right angle and less than a straight angle, so it is an obtuse angle.
By observing an angle we can only get the type of angle but to compare it properly we need to measure it.
To measure an angle using protractor
If two lines intersect with each other and form an angle of 90° then they must be perpendicular to each other.
If a perpendicular divides another line into two equal parts then it is said to be a perpendicular bisector of that line.
Here, CD is the perpendicular bisector of AB as it divides AB into two equal parts i.e. AD = DB.
Some of the 3D shapes around us
No. of Faces, Edges and Vertices in some common 3 D shapes
9 videos120 docs49 tests

1. What are some examples of threedimensional shapes that can be found in everyday life? 
2. How can you measure the length of a line segment accurately? 
3. How can you classify a triangle based on its angles? 
4. What is the difference between perpendicular lines and intersecting lines? 
5. How can you identify a polygon from other shapes? 

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