Mathematics Class VI

Knowing Our Numbers
Whole Numbers
Playing With Numbers
Basic Geometrical Ideas
Fractions
Integers
Decimals
Data Handling
Mensuration
Algebra
Ratio and Proportion
Practical Geometry
Symmetry

Measurement line

• A line segment is a fixed portion of a line. So, we can measure a line segment. The distance between the endpoints of a line segment is called its length. The measure of a line segment is a unique number. In fact, the measure of a line segment is called its length. It helps us in comparing two-line segments.

This can be done in several ways:

1. Comparison by observation

We can tell which line segment is greater than other just by observing the two line segments but it is not sure.

Here, we can clearly say that but sometimes it is difficult to tell which one is greater.

1. Comparison by Tracing

In this method we have to trace one line on paper then put the traced line segment on the other line to check which one is greater.

But this is a difficult method because every time to measure the different size of line segment we have to make a separate line segment.

1. Comparison by using Ruler and Divider

We can use a ruler to measure the length of a line segment.

Put the zero mark at point A and then move forward 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.

1. Put the one end of the divider on point A and open it to put another end on point B.
2. Now pick up the divider without disturbing the opening and place it on the ruler so that one end lies on ”0”.
3. Read the marking on the other end and we can compare the two line.

There are four main directions. They are North, South, East and West.

The turn from north to east is by a right angle. The turn from north to south is by two right angles. It is called a straight angle. If, we turn two straight angles or four right angles in the same direction, then it makes a full turn and we reach our original position. This one complete turn is called one revolution. The angle for one revolution is a complete angle.

We can see such revolution on clock faces. When the hand of clock moves from one position to another, it turns through an angle. Suppose the hand of a clock starts at 12 and goes around until it reaches 12 again. Clearly, it has made one revolution. It has turned through one complete angle or two straight angles or four right angles.

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