If r 1 and r 2 denote the radii of the two circles touching externally and ‘d’ is the
distance between their centers then, r 1 + r 2 = d.
The child may be provided with two embossed circles touching externally and he/she
may be facilitated to explore the distance between their centers. On exploration
assisted by the explanation by the teacher, the child will be able to understand the
concept.
- Circles touching internally
Two circles touching each other internally at a single point are said to be circles
touching internally.
If r 1 and r 2 denote the radii of the two circles touching internally and ‘d’ is the
distance between their centers then, r 1 - r 2 = d.
Two embossed circles touching internally may be provided and the child be allowed to
explore, and now the child will be able to realize that the distance between their
centers is equal to the difference of their radii.
Note : 1. If r 1 - r 2 < d, the circle with smaller radius will lie inside the larger circle.
- If r 1 - r 2 > d, the two circles lie seperately.
