Memory Pairs: a simple method for fewer turns

Twenty-four cards lie face down in front of you. How do you find all 12 pairs in as few turns as possible, without relying on luck? The answer is a fixed routine: always turn cards in the same order, never waste a second card, and keep only a few unmatched cards in your head at once.

The rules

In Card Lounge Memory Pairs, 24 cards are laid face down in a 6 × 4 grid. They form 12 pairs, and a pair is two cards of the same rank and the same colour, such as 7♥ and 7♦.

• Each turn, you turn over two cards.
• If they are a pair, they stay face up.
• If not, both turn back after a short pause.

The round is won when all 12 pairs are found. Your turns and your time are recorded, and there is no way to lose, so the only opponent is your own turn count.

Colour counts as much as rank

Clubs and spades are black; diamonds and hearts are red. A pair needs both the same rank and the same colour, so 7♥ and 7♦ match, but 7♥ and 7♠ would not, even though both are sevens. That also means you never need to remember the suit. "Red seven" or "black queen" is all the information a match depends on, and short names are easier to hold in memory.

A turn-by-turn method

Number the positions 1 to 24 in your head, reading row by row, and always explore unturned cards in that order. Then follow the same steps every turn:

1. First card: turn the next card you have never seen.
2. If its partner is already known: turn the partner. That is a pair, every time.
3. If its partner is not known: turn the next unseen card as your second card.
4. If that second card matches a card you saw earlier: you now know where a pair is. Collect it at the start of your next turn.

Never use your second card on a card you have already seen when it cannot match. It cannot make a pair, and it teaches you nothing new. A new card at least has a small chance of matching, and at worst it adds one more position to your memory.

How small is that chance? On the very first turn, once your first card is up, only 1 of the other 23 face-down cards is its partner, so a lucky match is 1 ÷ 23 ≈ 4.3%. Luck will not carry a round; memory does.

Worked example

Here are the first five turns of a round, using position numbers.

• Turn 1: position 1 is 9♥ (red nine), position 2 is Q♠ (black queen). No pair; both turn back.
• Turn 2: position 3 is 4♦ (red four). You have not seen its partner, so turn a new card: position 4 is Q♣, a black queen, the partner of position 2. It came as the second card, though, so this turn ends without a pair.
• Turn 3: collect the pair you know: positions 2 and 4. First pair found.
• Turn 4: position 5 is 9♦, a red nine. Its partner is at position 1, so turn that. Second pair found.
• Turn 5: position 6 is K♥ (red king). No partner seen yet, so turn position 7: J♠ (black jack). No pair.

After five turns you have two pairs, and three single cards to remember: red four at 3, red king at 6, black jack at 7. Seven positions have been seen, so 17 cards are still unseen.

Turn 3 might feel like a wasted turn, but it is not. Every pair needs one turn in which both of its cards are turned together, and a pair you already know costs exactly that one turn. You are never charged extra for knowing where things are.

Remembering positions

A few habits keep the load small:

• Say each card's short name and position quietly as it appears: "red nine, one".
• Forget a card the moment its pair is found. Matched cards stay face up, so you only need to track the unmatched singles.
• Keep exploring in the same order, so the cards you have seen are always a solid block at the start of the grid and the unseen ones a block after it.
• When only two cards are still face down, they must be a pair, because every other card has already found its partner.

Counting turns

Since each turn can find at most one pair, 12 turns is the fewest possible for a round. Because Memory Pairs records your turns and time, you can see whether the method brings your own count down from round to round. Compare yourself with yourself; there is no target you have to hit.

Try it

You have turned positions 1 to 14 so far. Five pairs are face up, and four cards are unmatched: 8♠ at position 3, 2♥ at position 7, K♣ at position 10 and 5♦ at position 12. Your next turn starts with position 15, which is 2♦. What do you turn as your second card? On the turn after that, position 16 is A♠. What then?

Answer: turn position 7. The 2♥ and 2♦ are both red twos, so that is a pair. On the next turn, A♠ has no known partner (8♠, K♣ and 5♦ do not match it), so turn the next unseen card, position 17.

Try the routine on Memory Pairs. If you enjoy reasoning about which cards are still unseen, read Higher or Lower: counting what is left, and browse every game on the games page.