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E:\Working\Focus_Learning\Math_Genius_4_(25-10-2023)\Open_Files\Chap-08
\\December 6, 2023 12:54 PM Bharat Arora P-6 Reader _________________________ Date: ___________________

How to Draw a circle?

A circle can be drawn simply by tracing the outline of

circular objects like a coin, a bangle or a cup, etc. To draw
a circle with given radius, we use a pencil, a compass and
a ruler.

Let us draw a circle of radius 3 cm.
Step 1: Place the pointed end of the compass at 0

mark of the ruler. Stretch the other arm of the
compass to 3 cm marking on the ruler. 3 cm

Step 2: Place the pointed end of the compass on the Centre of
paper and hold the upper end firmly. Rotate the the circle
pencil arm keeping pointed arm fixed.

relationship between the radius and Diameter of a circle

Look at the given figure.

Clearly, the diameter of a circle is two times the radius. Diameter

O
Diameter = 2 × Radius Radius Radius
If we know the length of a radius of a circle, we can find the length of
its diameter and vice versa.

example: Look at the given circles and find the missing measure.

(a) A (b) H
3 cm

O O ?
B C E F
? 8 cm

Solution:

(a) Radius (OA) = 3 cm (b) Radius (OH) = ?
Diameter (BC) = 2 × OA Diameter (EF) = 8 cm

= 2 × 3 cm That is, 2 × OH = 8 cm

= 6 cm So, OH = (8 ÷ 2) cm = 4 cm
Practice time 8D

1. Write true or false for the following statements.

(a) A circle is a polygon.

(b) All radii (plural of radius) of a circle are of equal length.

150 Mathematics-4