13
You only need
Assume the genuine coins weigh $x$ grammes.
Credit to Hexomino and Jaap for the corrections!
7
You always have a simple 50% strategy:
Whatever the opponent chooses, there are exactly 3 good spin results and 3 bad ones for you.
Your opponent always has a simple 50+% strategy:
Doing otherwise is always worse, or equal at best; there are no possible bullet configurations where there are more than 3 "good" spin results for the player going first.
...
3
The main thing to do here:
Now, to execute:
2
The number of weighings will be:
What will you do is to:
Mathematically speaking:
So the next step is:
Only top voted, non community-wiki answers of a minimum length are eligible
