Do you know why the area of circle is πr2 ?

The area of circle is  πr2 . How ?

What is  π ?

It is basically the ratio of circumference to the radius.

Example.

Half Circumference	22	44	66	88	110	132
Radius	7	14	21	28	35	42

According to the table  in any circle ratio of circumference to the radius is equal to  π.

If radius 7 then circumference must be 22.

For the area of circle

Let's do an experiment

1. Take a peace of paper.

2. Draw a circle of radius 7 cm.

3. Cut the Circle from the paper.
4. Divide this  circle in 12 equal parts as shown in figure by the help of protector and scale.
5. Cut these parts and set as shown in fig.

Now it is Showing like a rectangle but equal parts are blank so

The area of circle ia equal to the half of the area of that rectangle .

Area of the rectangle  shown in fig. is   2 πr ×r= 2πr2

Area of circle =  2πr2/2

            

                          = πr2