Concept:Equal circles arranged around a central circle of same radius form a hexagonal packing pattern.
Explanation:Let the radius of each coin be
r.
The centre of each surrounding coin must be at distance
2r from the central coin's centre.
Adjacent surrounding coins must also be
2r apart, so their centres form equilateral triangles with the central centre.
Each such equilateral triangle creates a
60∘ angle at the central centre.
Total angle around the central coin is
360∘.
Number of coins that fit
=60∘360∘​=6.
Thus, six coins can be placed around the central coin so that each touches the central coin and its adjacent coins.
Answer:D.
6