Page 93 - Start Up Mathematics_6

5 Understanding Elementary Shapes

Ananya along with her mother went to buy some tiles for
the kitchen. She had a specific design in her mind. She
wanted the tiles to be convex that had only acute angles.
The salesman boasted they had the largest collection of tiles
which includes triangular, square, rectangular, pentagonal
and hexagonal shapes. Can you suggest the shape Ananya
should look for?

In this chapter, we shall be dealing with measurement and comparison of line
segments and angles. We will also learn about types of angles, perpendicular
lines, classification of triangles on the basis of sides and angles, types of polygons
including quadrilaterals, regular and irregular polygons. Identification of some 3-D shapes will
also be taken up.

Comparison of Line Segments
Comparing two line segments means finding a relation between their lengths. The following are
some commonly used methods to compare two line segments:
(i) By observation

(ii) By tracing
(iii) By using a divider (an instrument in the geometry box)
Comparison by observation: In some cases, we can know by observation alone which line
segment is of greater length. Clearly, CD > AB.

A B

C D

Comparison by tracing: Let’s take two line segments PQ P Q
and RS that we cannot compare by mere observation. Trace
one of the line segments, say PQ, on tracing paper. Now, R S
place the traced copy of PQ on the other line segment RS,
such that P is placed on R and the two lines lie on each other.
R(P) S Q
Since Q goes beyond S, therefore PQ > RS.
Comparison by divider: A divider is a pair of pointers used to compare lengths. Let’s compare
two line segments PQ and CD.

(a) Put one end of the divider at P and open the divider such that the other end reaches Q.
(b) Without disturbing the opening of the divider, put one of its ends on C.
(c) Carefully mark the point along CD where the other end of the divider falls.