Page 71 - Maths Class 06

Elementary Shapes (2D–3D)

Introduction

In the previous chapter, we learned how to identify and define the basic terms of geometry such as point,
line, line segment, ray, etc. Let us now use some geometrical tools to measure and compare their sizes.

Measuring Line Segment

A line segment is a fixed portion of a line. It has two end-points, so its length can be determined. Let us
device few methods to compare the line segments.

Ways of Comparison Method Shortcomings

I. Comparison by observation A B P Q This method is not suitable if the
difference in lengths of the
Just by looking at the two line segments is very little.
segments ABand PQ, it can be
clearly stated that line segment
AB is larger than line segment PQ.
i e. . AB > PQ

II. Comparison by tracing A B P Q This method depends on the
Trace AB on the tracing paper and accuracy in tracing. Moreover,
place it over the segment PQ with tracing every line to compare the
A coinciding the point P. lengths of segments is a tedious
job.
Clearly it can be observed from
that, AB > PQ.

III. Comparison by using ruler A B P Q The thickness of the ruler may
Place the graduated side of ruler cause difference in reading, errors
along the line segment, such that can occur due to angular viewing
0 (zero) of the ruler coincides also. (positioning error)
C.M. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
with A. Read the mark on the
Inch.
5
4
6
3
2
1
ruler against the point B, the
length of AB can be determined
from the corresponding reading
on ruler. Similarly, proceed for
PQ and then compare.

71 Mathematics-6