# Memory Pairs: why a red seven never matches a black seven You turn over the 7♥, then the 7♠. Two sevens, and yet both cards turn back face down. In Card Lounge Memory Pairs rank alone is never enough: colour decides every match, and almost every grid is built so that this matters at least once. ## The rule, exactly In [Memory Pairs](../play/memory-pairs.html), 24 cards lie 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♦. Clubs and spades are black; diamonds and hearts are red. Each turn you turn over two cards. A pair stays face up; otherwise both turn back after a short pause. There is no losing condition, and your turns and time are recorded. Because each colour has exactly two suits, every pair is one heart and one diamond, or one spade and one club. The partner of the 7♥ is always the 7♦, and the partner of the 7♠ is always the 7♣. Every card in a grid is different, too, so you will never meet two 7♥. ## Four of a rank is normal There are 26 rank-and-colour combinations: red Ace, black Ace, red 2 and so on up to black King. Each grid uses 12 of them. So a rank can be missing, appear as one pair, or appear twice, as a red pair and a black pair: four cards of the same rank. That last case is the usual one. Across all 999,999 deals the game can produce, 99.4% contain at least one rank in both colours, almost three in four contain two or three such ranks, and a rare few contain six. Once you know that one colour of a rank is in the grid, the other colour is there too about 44% of the time. So when you see a seven, do not file it under "seven". File it under "red seven". ## Name cards by colour and rank Suit tells you nothing beyond colour, so drop it. "Red seven at 4" and "black queen at 11" hold everything a match depends on, and short names are easier to keep in your head. Say the colour first: when a rank turns up in both colours, colour is the only word that separates the two pairs. ## Worked example Number the positions 1 to 24, reading row by row. - **Turn 1.** Position 4 shows 7♥ and position 9 shows 7♠. Same rank, different colours: no pair, and both turn back. Look at what that turn taught you. The grid holds two pairs of sevens, and both partners are still hidden: the 7♦ belongs with position 4 and the 7♣ with position 9. You are now tracking two singles of the same rank, "red seven at 4" and "black seven at 9". - **A later turn** starts with the 7♦ at position 15. It is a red seven, so its partner is position 4. Turn it: pair. - Had you remembered only "a seven at 9" and turned position 9, you would see 7♦ and 7♠, no pair, and a whole turn spent showing you two cards you already knew. - **Later still**, the 7♣ appears at position 20 as the first card of a turn. It is a black seven, so turn position 9: pair. Played this way, each of the two seven pairs costs exactly one turn once its second card shows up. Mixing up the colours costs an extra turn every time it happens. ## Quick checks that save turns - Read the colour before you choose your second card. - Treat each single as one exact card. "Red seven at 4" means you are waiting for the 7♦ and nothing else. - If you think you have seen the same card twice, your memory has slipped somewhere, because every card in the grid is different. - Do not assume the other colour exists. Seeing a red seven tells you nothing certain about black sevens until one appears. - Matched cards stay face up, so glance at them to see which rank-and-colour pairs are already gone. ## Try it Four cards are known and unmatched: 10♥ at position 3, 10♣ at 8, J♠ at 11 and Q♦ at 17. Your next turn starts with position 18, which is the 10♠. Which card do you turn second? And how many tens can still be hidden? Answer: position 8. The 10♣ and the 10♠ are both black tens, so they are a pair. The 10♥ at position 3 is red and waits for the 10♦. Exactly one ten is still hidden, the 10♦, because a rank can appear in at most two colours and each card only once. For a full turn-by-turn routine, read [Memory Pairs: a simple method](memory-pairs-method.html), and look up any term in the [glossary](../glossary.html).