# Hidden Agenda | Dollar Deal

By Roberto Giobbi - Friday, September 6, 2019

## From Hidden Agenda, April 16th

Dollar Deal Apr 16th

Arrange the deck into red/black alternating order. Show the order by ribbon-spreading the deck face up, and then turn the spread face down using the Ribbon Spread Turnover Flourish.

Now propose the following bet: The spectator may insert the bill anywhere into the spread, and then deal the cards in pairs from the top of the face-down deck until he reaches the bill. If the card that forms a pair with the bill is a red card he wins, if it is a black card you win. This is apparently a 50:50 proposition, but actually it is a scam and you always win.

When ribbon-spreading the cards, simply look at the color of the top card; if it is a black card, black wins, if it is a red card, red wins, always.

This is completely counterintuitive and you have to try it in order to understand what happens. However, courtesy of Bob Farmer, here is the explanation by mathematician, Professor Robin Dawes: “This is like a minimalist Gilbreath Principle: the inserted bill either goes in before or after a card in an odd-numbered position. If it goes in before, it becomes the first part of the pair containing that card. If it goes in after, it becomes the second part of the pair containing that card. Either way, it will be paired with that card - and if the cards in the odd-numbered positions are all the same color, you can be sure of the color of the card the bill is matched with.”

This is the basic idea and it stems from that creative genius Bob Hummer.

Can you come up with an even more deceptive handling and presentation? Is it indispensable to mention the alternating color order at the beginning? How would you then get into the necessary setup?

All entries from this series come from Roberto Giobbi's Hidden Agenda book.

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