1) The document discusses the key terms related to circles - radius, diameter, circumference, and area. It provides definitions and formulas for calculating each. 2) Examples are given to demonstrate calculating the radius given the diameter, and vice versa. It also shows calculating circumference given diameter or radius. 3) Practice questions are provided for readers to calculate diameters from radiuses and circumferences from diameters using the formulas.

1. Circle
Radius, Diameter and Area
Presented By: Zeeshan Ali Mangi

3. Bicycle
Bike
Car
Bus
Aero plane
Swimming Pool
Circular Park

4. And so on like such examples in our daily life

5. Radius:
• Radius(r)= Diameter/2 or r=d/2
r
r r
• Any point from a circumference to the center of
circle is called Radius.
• It makes a small line segment.

6. Question
Q:1 if the diameter of a circle is 4cm then find its Radius?
r=d/2
r=4/2
r=2cm Ans:

7. Practice Questions
If the diameters of different circles are given below then find their
Radiuses?
Q: 10m
Q: 30cm
Q: 40km

8. r r
Diameter
• Diameter(d) = 2Radius or d= 2r
Diameter
• Any two points from a circumference to the
center of circle is called Diameter.
• It makes two small line segments.

9. Question
Q:1 if the radius of circle is 2cm then find its Diameter?
d=2r
d=2(2)
d=4cm Ans:

10. Practice Questions
• If the radiuses of different circles are given below then find their
diameters?
Q: 3m
Q: 4cm
Q: 6km

11. r
Circumference
• Circumference(C) = d∏ or 2∏r
Circumference or Perimeter or Circular boundary
d
Where d is diameter Where r is radius

12. Question
if the diameter of a circle is 7cm then find its circumference
C= 2∏r or d∏
C= d∏ where pie is approximately equal to ∏=22/7
C= 7(22/7)
C=22cm Ans:
Or r=d/2
r=7/2
C=2 ∏ r
C=2 ∏(7/2)
C= ∏ 7
C= (22/7)7 =22 Ans:

13. One interesting Fact about Circle

14. 8 parts
64 parts
32 parts
16 parts
Parallelogram

15. Area of Circle
• Circumference(C) = 2∏r
Half circumference = ½(2∏r) = ∏r
Width
Length
Circle

16. r
Half Circumference = ∏r
Radius = r
Area of a Circle = ∏r2

17. Q: If radius of a circle is 7cm then find its area?
Solution:
Area of a circle = ∏r2
= ∏(7)2
= ∏(49)
= (22/7)49
=22/7 Ans:

18. Q: If a person wants to travel 3km by a car, if the radius of a car’s tire is 5m then find
after how many rotations, it will cover that distance?
Solution:

19. Word Problem
r
7m (Width of the road)
• Find the area of the road and repairing it at the cost of 2m2/ ?
21m (radius of external
circular Walking track)