Washington Post Staff Writer

The Math Club's method of winning at blackjack is not unique in the annals of gaming. Over the years mathematicians and computer experts realized that certain cards--the 9s, 10s (including face cards that count as 10s) and aces--were more valuable than other cards to blackjack players. And there were ways to know when a deck was "fat" in those cards.

The Math Club chose a relatively simple method to "count," or keep track of, those valuable cards.

To begin with, Bradford Hanes and his colleagues ignore all 8s that are dealt. All 2 through 7 cards are assigned a value of plus one. The good cards, the 9s, 10s, and aces, are assigned a value of negative one. Then, as each card is dealt by a dealer, Hanes keeps a mental count, as in, "minus one, even, plus one ..."

Nothing attracts the attention of the casino management faster than a head bobbing up and down as each card is dealt; that's a sure sign of an amateur counter. The pro wants to appear natural, unconcerned about other players' hands. When all cards are dealt, Hanes counts the cards in pairs at a glance, and determines the running count.

A high negative count means many of the favorable cards, the 9s, 10s and aces, have been dealt and therefore bets should be decreased. A positive count means the deck is rich with attractive cards, so it's time to increase bets.

The sophisticated counter wants to know more than the running count; he wants to know the true count, or "count-per-deck-remaining." In other words, in a multiple deck game just beginning, a plus one count means little because only a few cards have been dealt. But when a shoe has been dealt down to the last couple of decks, the count takes on a greater importance.

To determine the true count, divide the running count by the estimated number of decks still to be played. For example: With a plus one card dealt off the top of a six-deck shoe, the true count is one-sixth. But a plus one count with one deck left to deal, means a true count of plus one.

"When the true count gets above one, you're playing with an advantage you can take to the bank," says Hanes. "When the true count gets above two, you've got a bigger advantage. When it gets above three, the casino is giving you money. If you can play all day with a true count above three, you're playing with a three per cent advantage. Betting $100 at at time, you'll be rated to make $3 a bet. At 100 hands an hour, that's $300 per hour."