This article originally appeared in the Winter 1980 issue of Gammon Magazine.
It later appeared in the December 1999 issue of GammOnLine.
Thank you to Bill Davis and Kit Woolsey for their permission to reproduce it here.

The Great Prime Problem

By Bill Davis
The climax of each Friday evening Coastal Backgammon Club meeting is the late night money match between the Man and the Kid. There are always three principle character elements in this high stakes contest.

The Man is a dapper gentleman of nearly sixty years, possessing a methodical, yet creative style of play. Outwardly, he appears unconcerned with whether he wins or loses. For him, the game is a mental exercise to benefit his problem solving capabilities.

The Kid is a smart, young newcomer to the game with a rocket-like manner of play. His success stems from an intense desire to defeat his opponent; however, there are times when this strong desire gets in his way.

The spectators make up the third element of the match adding electricity to the air. For them, the confrontation is more than just a money game—it's a battle of wits.

On this particular Friday night, the net match score remained very close. After two hours of intense play, the Man had his young rival by only eight points. The next game made the contest a monetary stalemate as the Kid bagged a redoubled gammon.

Five minutes later, the crowd of onlookers had doubled and strangely enough, neither player had thrown the dice. One of the regular spectators wandered over to the front table where the club director was seated.

"I'm not sure, but I think the old Man is hustling the Kid again."

"What's happening this time?" questioned the director.

"Just as they had completed the setup for a new game, the Man made an unusual challenging statement. He said that from the opening position, given four legal moves in a row, he could trap the Kid's back men behind a six point prime."

The director looked puzzled. "Let me see if Išve got this straight. From the normal opening setup position, the Man will have any four legal moves of his choice, doubles included, to build a six point prime. I assume the Kid's pieces don't move."

"Correct," replied the spectator.

The director walked over to a vacant board and set up the starting position. Within a minute he had built the required prime.

"Here's a very simple sequence that does the trick." The director began to move the pieces as he showed the spectator his solution. "Make the bar and 5-point with 1-1; grab the 4-point with a 4-2; from the midpoint, bring two men down to the 8- and 9-point with 5-4; and complete the prime with another 5-4 throw, covering both blots. It's simple. I'm sure there are many ways to do it. Don't tell me the Kid missed this!"

"No, he found that line all right," responded the spectator. "But then the Man brought money into the picture. He wagered the Kid that he could build a prime (a Great Prime, he called it) with only three moves and that it would overlay his 2-point through bar point inclusive."


Starting Position


Great Prime

Again, the director set up the board and began sliding the pieces into a variety of positions. After five minutes of fruitless effort, he sat back.

"The prime is just too deep into my home board to be built with only three moves. I say it's impossible."

Suddenly from across the floor, the Kid pounded his fist on the table, stood up, threw a couple of large bills toward the man and steamed out of the room.

"I guess the Kid said the same thing," smirked the spectator.

The problem is to construct the previously defined "Great Prime" in only three moves (doubles permissable).

Solution will appear next month.

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