 Hi and welcome to the session. Today we will learn how to measure line segments. Now all the shapes that we see around us are formed using curves or lines. So today we will learn how to measure line segments. So for that let us see what is a line segment. A line segment is a fixed portion of a line. For example this is a line say line L. And if you mark two points say A and B then the fixed portion A, B is the line segment A, B. Now the distance between the end points that is A and B over here of a line segment is its length. So if we want to compare any two line segments then we find the relation between their lengths. So now we can compare two line segments by observation. That is by just looking at them we can see that which one is longer. Also we can compare two line segments by tracing and for this we use the tracing paper. And thirdly we can compare two line segments using a ruler and a divider. Now let's see how to compare two line segments using ruler and a divider. Now you must be having a ruler in your instrument box. A ruler is divided into 15 parts. And each of these 15 parts is of length 1 centimeter. So we can say that one part is equal to 1 centimeter. And each of these centimeters that is 1 centimeter is divided into 10 sub parts. And each sub part of the division of a centimeter is 1 millimeter. So here we have one sub part is equal to 1 millimeter. Now 1 centimeter is divided into 10 sub parts and each sub part is 1 millimeter. So that means 1 centimeter is equal to 10 millimeters. And from this we can also say that 1 millimeter is equal to 0.1 centimeter. Now suppose we want to write 2 centimeter and 7 millimeters into centimeters. Then this will be equal to 2 centimeters and 7 millimeter will be equal to 0.7 centimeters. So this is equal to 2.7 centimeters. Also if we are given 3.2 centimeters then this will be equal to 3 centimeter and 2 millimeters. Now suppose we are given this line segment let us name it as AB and we want to measure its length. So for this take the ruler and place the zero mark of the ruler at point A. And then read the mark against the point B. This will give you the length of line segment AB. Now here the length of line segment AB is equal to 5.4 centimeters. Now let's see how to measure the length of this line segment using the divider. First of all open the divider, place the end point of one of its arm at point A and the end point of second arm at point B. Now taking care that the opening of the divider is not disturbed lift the divider and place it on the ruler. Now place one end point of the divider at the zero mark of the ruler and then read the mark against the other end point. So this will also give you the length of the line segment AB as 5.4 centimeters. Now let us learn about angles. When a hand of a clock moves from one position to another position say here then we have an example of an angle. So here this is an angle. Now one fourth turn of the hand is known as a revolution and this is known as a complete angle. Next one fourth revolution of the hand is known as a right angle and lastly half revolution is known as a straight angle. Straight angle is also equal to two right angles. From here till here we have one right angle and from this till this point we have second right angle. Now let's see what is a acute angle. Angle smaller than a right angle is called a acute angle. Now here we have a right angle. So the angle smaller than a right angle that is this one is an acute angle. Now let's see an obtuse angle larger than a right angle but less than straight angle is known as an obtuse angle. Now here we have a right angle and a straight angle. So the angle larger than a right angle but less than a straight angle that is this one is an obtuse angle. Now lastly let us see what is a reflex angle larger than a straight angle is a reflex angle. So here this is a reflex angle. This angle is greater than a straight angle. With this we finish this session. Hope you must have understood all the concepts. Goodbye take care and have a nice day.