Solution:
The Statement about two circles is :
1. The two circles are congruent.
2. Let One circle be
and another circle be
.
Shaded Part of
=

It means three out of four parts is Shaded.
Non Shaded part of
=1 -
=

Shaded Part of
=

It means two out of three part is Shaded.
Non Shaded part of
=1 -
=

From , Above information we can't draw conclusion that in how many parts or in pieces a circle can be divided.
From , my point of view his sister is incorrect.
If we want to divide a circle , it totally depends on us in how many parts we want to divide it. So, we can't predict the least number.