Page 135 - Math Genius C5

E:\Working\Orange_Education\Math_Genius_5\Open_Files\CHAP_06
\ 08-Oct-2025 Bharat Arora Proof-9 Reader’s Sign _______________________ Date __________

Š Radius: The distance from the centre to any point on the Radius (OC) Circumference
boundary of the circle is called its radius. C
Here, OC, OA and OB are the radii of the given circle. Centre (O)

Š Diameter: The distance between two points on the A O B
boundary of the circle that passes through the centre is Diameter (AB)
called its diameter. Here, AB is the diameter of the given

circle.

Š Circumference: The distance around a circle is called Math Insight
its circumference. A circle can have infinite

Š Relation between Radius and Diameter: The diameter radii. Radii is the plural of
of a circle is twice the radius of the circle. The radius radius.
of a circle is half the diameter.
Knowledge Desk
Diameter = 2 × Radius
or The distance between any two points
on the boundary of a circle is called
Radius = Diameter a chord of a circle. The diameter is
2 the longest chord of the cirlce

Example 1: Find the diameter of a circle whose radius is 6 cm.
p u Z Z L E Critical Thinking
Solution: We have: Diameter = 2 × Radius Connect all
Therefore, Diameter = 2 × 6 cm = 12 cm. the given dots

Example 2: Find the radius of a circle whose diameter is 8 cm. without lifting
your pencil using
Diameter exactly four line
Solution: We have: Radius =
2 segments.
8
Therefore, Radius = = 4 cm.
2

maths fun Critical Thinking

Playing with Circles
• Draw a circle with a compass and mark its centre.

• Draw its diameter. Mark the endpoints of the diameter.
• Draw another diameter of the circle and mark the endpoints.
• Now join the four points.

What shape is formed? Check the sides of the quadrilateral and
the angles obtained.
What do you notice about the shape that is formed?

Is it possible to create a 4-sided shape other than the shape shown here through
this process?

Mathematics-5 133133
Mathematics-5