AND STUDENTS

ActivityMathematics

IN

Area of circle

Presented byh. p. patelTgt maths

Objective

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

Pre requisite knowledge

• Radius and circumference of the circle.• Equal parts of the circle.• Area of the rectangle.

Materials required

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

ProcedureDraw 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.

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.So Length of parallelogram=πr.And breadth = r.

πr

πr

r

r

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.

So, area of parallelogram(rectangle) = length x breadth = πr x r = πr2

πr

πr

r

r

Result Area of a circle with radius r is πr2.

r

Area of circle = πr2

Test your knowledge1. 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.

Thanks