This document defines key terms related to circles such as radius, diameter, and circumference. It states that in a circle, every point is equidistant from the center. The radius is the distance from the center to any point on the circle, while the diameter is a line segment that passes through the center and touches two points on the circumference. It provides examples of how to calculate the radius given the diameter and vice versa. The document also notes the approximate relationship between circumference and diameter of a circle.

1. The Circle
By Ranjana

2. O A
CIRCLE
Eg. ball,bangle,lemon.coin

3. O
A
CENTRE : O
RADIUS : OA
B
CENTRE
RADIUS

4. .O
In a plane,each point of the circle is at equal
distance from a fixed point.The fixed point is
called the centre of the circle.
CENTRE = O

5. O
The distance from centre to any point on the
circle is called radius of the circle.
A
RADIUS = OA
Radius

6. .O
DI
A
M
E
T
E
R
A Line segment passing through the centre of
the circle and whose end points lie on the circle
is called the diameter of the circle.
A
B
DIAMETER = AB

7. .O
The length of the circle or the distance
around it is called circumference of the
circle.

8. .O
A B
A Line segment whose both the ends touches
the circumference and passes through the
centre is called diameter.
DIAMETER : AB

9. Relation between radius and
diameter
.O
A B
RADIUS = DIAMETER
2
OB = AB
2

10. Eg. If diameter of the circle is 10 cm then find
its radius?
.O
Diameter = 10cm
Sol. Radius =diameter / 2
radius=10 cm/ 2
radius =5 cm
A B

11. .O
Eg. If radius of the circle is 6 cm,then find the
diameter of the circle?
Radius = 6cm
A
Sol. Diameter = 2 x Radius
Diameter = 2 x 6cm
Diameter = 12 cm

12. RELATION BETWEEN CIRCUMFERENCE AND
DIAMETER
.O
DIAMETER
CIRCUMFERENCE = 3 x DIAMETER(APPROX)
A B

13. Eg. Find the circumference (approx) of the circle whose
diameter is 10cm.
.O
DIAMETER=10 CM
Sol. Circumference = 3 x
diameter(approx)
Circumference = 3 x 10 cm
Circumference = 30 cm
A
B

14. EVALUATION
1. what is the relation between radius and diameter of the
circle?
.O
A B
2. What is the relation between circumference and diameter
of the circle?
3. In this figure
Sol .Radius=diameter/2
Sol. Circumference=3Xdiameter(approx)
radius
diameter
centre
AB is ________.
O is _________.
OA or OB is ______.

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