Class 6 · Chapter 5

Understanding Elementary Shapes

Measuring line segments and angles; perpendicular and parallel lines; classification of triangles and quadrilaterals; 3D shapes.

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Tip: open the NCERT PDF for the original chapter text alongside the notes here.

Detailed theory

Use a ruler and place the

0

mark at one endpoint; read the mark at the other. Compare segments by superimposing (paper folding) or by measurement.

Key concepts & formulas

Perpendicular lines meet at

90^\circ

; parallel lines never meet.

Triangles by sides: equilateral, isosceles, scalene; by angles: acute, right, obtuse.

Sum of angles of a triangle

= 180^\circ

A cube has

6

square faces,

12

edges,

8

vertices.

A cylinder has

2

circular faces and

1

curved surface.