area of circle

3. Area of circle
Presented by
h. p. patel
Tgt maths

4. Objective
To find out the area of a circle through
paper cutting and pasting method.

5. Pre requisite knowledge
• Radius and circumference of the
circle.
• Equal parts of the circle.
• Area of the rectangle.

6. Materials required
• White sheet of paper.
• Glazed papers.
• Geometry box.
• Fevicol/gum.
• Scissors.

7. Procedure
 Draw a circle with radius r (10 cm).
 Divide the circle in 16 equal parts.
 Radius of the circle = r.
 Circumference of circle = 2πr.
 Length of green circum. = πr.
 Length of pink circum. = πr.

8. Procedure continue -
 Cut all the sixteen parts of circle with scissor and
arrange them as shown in figure.
 Length of green side = πr.
 Length of pink side = πr. πr
 So Length of parallelogram=πr.
 And breadth = r. r
r
πr

9. Observation
 From above activity we can observe that, if we will
make small part of circle and rearrange them like a
parallelogram , it become a rectangle with length πr
and breadth r. πr
 So, area of parallelogram
(rectangle) = length x breadth r
= πr x r r
= πr2
πr

10. Result
Area of a circle with radius r is πr2.
Area of circle = πr2
r

11. Test your knowledge
1. Find the area of a circle with radius 7 cm.
2. Find the area of a circle, if circumference of the circle
is 132 cm.
3. Find the radius of a circle, if area of the circle is
154 cm2.