Two or more embossed concentric circles be prepared on a sheet of paper and the
child be asked to explore. Tactually, the child can observe that all the circles have the
same centre but different radii thus enabling him/her to understand the concept of
concentric circles.
- Circular ring
If two circles with the same center and different radii are drawn on the same plane,
then the portion between the two circles is called as ‘circular ring’.
The procedure adopted for explaining the idea of concentric circles may be repeated
with the additional information on the idea of circular ring, which is nothing but the
area formed between the two concentric circles.
- Area of a circular ring
Area of a circular ring = π (R^2 – r^2 ), where R is the radius of the outer circle and r is
the radius of the inner circle.
As the child is already familiar with the idea of circular ring, the formula for finding
the area of the circular ring may be explained orally. To enhance the understanding
level of the child, he/she may be asked to find out the area of a few circular rings on
his/her own after the demonstration by the teacher.
- Intersecting circles
Two circles having some part of their area common between them are called as
intersecting circles. In other words, two circles intersecting each other at two points
are said to be intersecting circles.
Let r 1 and r 2 be the radii of two circles and let ‘d’ be the distance between their
centers.
o r
R
