There is a fairground/fundraising con based on this. Customer gives you one or two dollars. You set up a card to keep track of a set number of coin flips - 10

There is a fairground/fundraising con based on this. Customer gives you one or two dollars. You set up a card to keep track of a set number of coin flips - 10 say. The deal/catch: - heads = multiply their money by 1.25. - tails = multiply their money by 0.78. People will usually see +0.25 payout vs -0.22 cost instead of the actual fractional payout as you've already noted. The nice thing, is one person flips a coin and is the crowd pleaser, while another is the note taker. People can join at any time.