Page 171 - Start Up Mathematics_4

Open and Closed Shapes

Look at the following shapes. They start and end at different points. They are called open
shapes.

Now, look at these shapes. They are closed shapes. They start and end at the same point.
They are enclosed by a boundary on all sides.

Polygons

Polygons are closed shapes made with line segments joining only at their end points. They
always have more than two sides. A triangle is a polygon with 3 sides. A polygon with
4 sides is called a quadrilateral. The point where two sides of a polygon meet is called a
vertex.

Triangle Remember

A
The given triangle is a polygon
with sides AB, BC and AC and A triangle is a polygon with
least number of sides.
vertices A, B and C.

B C

Quadrilateral

There are various types of quadrilaterals. Some of them are:
1. Rectangle 2. Square 3. Rhombus 4. Trapezium

In this class we will study about rectangle and square.
Rectangle: A rectangle is a quadrilateral with two long and two short sides.

length (longer side)
A B
Try This!

Take a pencil box. Keep it on
breadth breadth a sheet of paper and trace
(shorter side)
its outline (or boundary).
What shape do you get?
D length C

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