Activity ix 2
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This document describes an activity to calculate the area of a circle using paper cutting and pasting. It involves drawing a circle, dividing it into 16 equal parts, cutting out the parts and rearranging them into a parallelogram. This shows that the area of the circle is equal to the area of the parallelogram, which is πr x r or πr2, where r is the radius of the circle. The document concludes that the area of any circle is πr2.
Activity ix 2
- 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.