how many smaller circles(radius is equal) I can fit within a larger circle

Question

then the question is,the larger radius D,the small radius d,get the largest number of small circle put in the larger?

Answer 1

The answer can be closely approximated by this equation:

Number of Circles $= 0.83\frac{R_2^2}{r_1^2} - 1.9$ (rounded down to whole number)

where: $R_2$ = radius of larger circle $r_1$ = radius of smaller circle