This Darts - 501 Scores equation computes the value of a "throw" in the dart game of 501, which is often played in league competition in America. The player in the game of 501 subtracts the value of his three darts thrown on his turn from a starting score of 501. Since the first player to reach zero points is the winner, the player will attempt to throw the highest total of points from three darts on most turns.
The board has radial sectors for each number 1 through 20 and these radial "slices" of the dart board are ringed on the outermost edge by a ring that doubles the slice value. A concentric ring closer to the bullseye triples the players slice value. So, for instance the highest single dart score possible is 60 points, which occurs when the pl
ayer hits the triple ring over the 20 slice with a single dart. And that, of course means the largest score player can make on a single turn is 180 points, three triple 20s, also referred to as a "ton-80".
The bullseye itself is considered a single "bull" and is worth 25 points. The ring immediately around the bullseye is considered a double bull and thus worth 50 points.
Pull yer prickles, mate!
Notes
Strategy for 501
The game of 501 starts with each player having a score of 501. Players take turns throwing three darts and each turn the total points for their three darts is added up and the total points for the three darts are subtracted from what remains from their last turn. So, for instance if they throw a triple 20, a double 20 and a single 1 on their first throw, the sum of their darts score would be 60 + 40 +1 = 101 and the score of 101 for that first turn would be subtracted from 501 leaving them with 400 points. On the next turn whatever their darts add to would be subtracted from 400 points.
At the beginning of the game most players strive to score the highest combination of points possible each turn. Thus the ultimate perfect throw of three darts on a turn is three triple-20s, which sums to 180 points. The real strategy comes into play when the player bring their score to 170 points or less because a key element of the game is that the player must double-out.
To double-out means the player must end the game by hitting the last dart on a double score: the outer ring of any number 1 through 20 or the innermost bullseye. The outermost ring is the doubles ring and scores double the numeric value of the sector.
Thus hitting the outermost double ring of the sector that is the number 5 scores ten points. If a player had exactly ten points remaining on his score and that player hit the double 5, that player would win. You must double out in 501.
The value 170 is a critical value in the game because at 170 point is the first time the player has the opportunity in a single turn to double-out and win. If a player were to arrive at 170 points, and then on their turn hit triple-20, triple-20 and double bullseye, they would score 170 points AND double-out to win!
The double bullseye is the innermost bullseye. The ring immediately around the bullseye is the single bullseye (worth 25 points).