BEST COIN TO MINE WITH A RASPBERRY PI

Answer: none, that's not what a raspberry pi is for if you want to mine you really need to get an actual miner, you'll end up spending more on your power bills than what you will gain from mining. Even with a computer specifically built for mining chances are unless you live in an area where power is cheap you're still not going to be making much off it.

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... Also you have a high probability of frying your pi's CPU so at the end of the day you'll just be out another $30.