N & gt=[(R^2)/(4r^2)]
Where [x] represents the smallest integer not less than x, for example, [2.5]=3,
It can be verified that if R= 1, r= 1, that is, the two circles are equal in size, n >；; = 1
So the answer to this question is N=2500/4=625.
Let point A be a plane fixed point in a small circle with radius r; Move the small circle so that A is always in the circle, then the maximum moving range of the small circle is a circular area with A as the center and 2r as the radius.
In other words, point A must be in any small circle falling into the 2r region.
Next, it is enough to calculate how many such regions are in the great circle of R, that is, [(r 2)/(4r 2)] (integer).
The sixth floor doesn't understand what I mean, it's not tangent, and it can't be drawn at all I will make a chart.
Newcomer, love the connection of mathematics.