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# Summary

7th Maths : Term 2 Unit 2 : Measurements : Summary

Summary

● Circle is a round plane figure whose boundary (the circumference) consists of points equidistant from the fixed point ( the centre).

● Distance around the circular region is called the circumference or perimeter of the circle.

● Circumference of a circle, C = πd units, where ‘d’ is the diameter of a circle and π = 22/7 or 3.14 approximately.

● Area of the circle is the region enclosed by the circle.

● The area of the circle, (A) = π r2 sq. units, where ‘r’ is the radius of the circle.

● Area of the circular path = Area of the outer circle – Area of the inner circle

= π R2π r2 = π (R2r2 ) sq. units, where ‘R’ and ‘r’ are radius of the outer and inner circles respectively.

● Area of the rectangular path = Area of the outer rectangle – Area of the inner rectangle

= (LB lb) sq.units, where L, B, and l, b are length and breadth of outer and inner rectangles respectively.

ICT Corner

Expected Result is shown in this picture Step-1 :

Open the Browser type the URL Link given below (or) Scan the QR Code. GeoGebra work sheet named “Mensuration” will open. There are two activities named “Area by Activity” and “Circular path problem”

Step-2 :

In the first activity move the slider n (No. of divisions) and the slider r (to increase the radius). As the no. of division increases it becomes almost a rectangle with Length = half the circumference and breadth equal to the radius. Thus the area = Length × Breadth = πr2. Also try the second activity. 