Procedure - Area of the Circle is half the product of its Circumference & Radius, Class 9 Math | Extra Documents & Tests for Class 9 PDF Download

As performed in real lab:

Materials required:

Coloured paper, compass, scale, a pair of scissors, gum, colours

Procedure:

• Draw a circle of radius r = 4 cm (say) on the paper.

• Divide the circle into 16 equal parts. [Fig (a)]

• Cut all the 16 parts and arrange them to get the [Fig (b)].

• Take any part from any side and further divide it into 2 parts. [Fig (c)]

• To complete the shape of rectangle arrange these two smaller parts at the corners of the shape obtained in [Fig (b)].

• Find the length and the breadth of the rectangle so formed [Fig (d)].

• Find the area of the rectangle.

          Fig (b)

         Fig (d)

As performed in Simulator:

• Click on scale (between 2 and 3) in workbench to draw circle.

• Click on the circle to mark 16 sectorials parts & color them differently.

• Move mouse over each wedge to align them in a row.

• Click on next button below to color wedges & divide in two group.

• Click blue group to rotate and align.

• Drag the blue group and drop over green group to join and form parallelogram.

• Click on left most wedge to cut it into two parts.

• Drag the red part and attach to the right end so as to form a rectangle.

• This is a rectangle whose area can be calculated as (Length x Breadth).

Observations:

• The students will observe that the area of rectangle  

• The students will observe that the rectangle is obtained from parts of circle. Hence area of circle = π x r²