Brainstorming with 4 Cards: Why 'Make 24' is the Ultimate Tool for Number Sense
January 12, 2026
From a flash of inspiration by a Chinese-American inventor to a global math competition. Discover how the Make 24 game trains your working memory and builds amazing mental math intuition.
Categories：Popular Science
Do you remember your childhood summer vacations? In those days without smartphones or iPads, a simple deck of playing cards could keep us entertained for an entire afternoon.
Draw 4 cards, and whoever calculates 24 first wins the cards—this was probably the earliest "esport" for our generation.
Back then, we just thought it was fun and exciting. But as we grew up, we realized that this seemingly simple number-crunching game is actually a sophisticated brain training system. It’s not just about arithmetic; it’s about training a high-level ability called "Number Sense".
Who Invented This "Torturous" Game?
While similar counting games have long existed in Chinese folklore, the man who standardized it into a competitive sport and introduced it to the world is a Chinese-American inventor named Robert Sun.
Inspired by 1960s Shanghai
Mr. Sun recalls that the inspiration for the game came from his childhood in Shanghai. Resources were scarce back then, and playing cards were one of the few entertainments for children. By 1988, living in the US, he noticed that many American kids hated math, so he remembered this childhood game.
How Did It Conquer the World?
He didn't just write down the rules; he designed those special square cards. This game quickly swept through tens of thousands of classrooms in the US. Teachers found it much more effective than boring worksheets! To win, kids would spontaneously perform hundreds of mental calculations.
Why 24?
Have you ever wondered why not 20 or 30? Because the number 24 is simply perfect. It has 8 factors: 1, 2, 3, 4, 6, 8, 12, and 24! This means there are many paths to reach it, and the difficulty is just right—neither too obvious nor impossible.
What Exactly Does It Train?
If you think it's just about the speed of addition, subtraction, multiplication, and division, you are underestimating it. It trains the underlying hardware of your brain.
1. Expanding Your "Working Memory"
When playing, you need to "temporarily store" several numbers in your head while processing others.
- "I have 3, 3, 8, 8... okay, 8 minus 3 is 5... no, what do I do with the remaining 3 and 8?" This process is like a stress test for your computer's RAM. People who play often significantly increase their brain's "RAM," making them less likely to "crash" when handling complex problems.
2. Cultivating "Intuition for Numbers"
An expert sees 3, 3, 8, 8 and doesn't calculate blindly. Their intuition immediately screams: "8 divided by (3 - 8/3)".
Usually, intuition looks for 3x8 or 4x6. This ability to jump straight to the answer without logical deduction is Number Sense. It is crucial in finance, programming, and even poker.
3. Practice of Reverse Thinking
Ordinary people calculate from left to right. But in this game, you need to stare at the result (24) and reverse-engineer the process. This "End in Mind" (reverse engineering) thinking pattern is key to solving many of life's problems.
Have you encountered an unsolvable hand?
Don't doubt yourself; some card combinations are indeed unsolvable! But in a standard game (using cards A-10), the probability of a solution is not 100%. If you can't solve it, don't force it; the question might just be playing tricks on you.
How Many Can You Solve Now?
Maybe your calculation speed isn't as fast as it was in elementary school, but your strategic thinking might be stronger.
No need to look for a deck of cards; we have recreated this classic mental gym for you. Not only does it generate questions, but if you really get stuck, one click will show you all possible solutions (yes, sometimes there's more than one!).
🔗 Open Make 24 Calculator
Enter your 4 numbers or generate a random hand. See if your brain is still sharp?
Universal Formulas to Make You Look Smart
Finally, here are a few tricks for those pulling their hair out over this game:
- Use 0 and 1: If you have two identical numbers, like
5, 5, you can turn them into 1(5/5)or 0(5-5). This is very useful for assembling numbers. - Focus on 3 & 8, 4 & 6: As long as you have these numbers, see if you can make the remaining cards form their "other half."
- Don't Forget Fractions: Many legendary hard problems (like
1, 5, 5, 5) require fractions.5 * (5 - 1/5) = 24. Saying this solution out loud will definitely impress everyone.
Conclusion
This game proves one thing: Math doesn't have to be boring formulas; it can be a creative art.
Even if you don't need to compete, playing this game occasionally to give your brain some "aerobic exercise" is a fun way to fight against a mediocre life. Come on, deal the cards!
Produced by the iknowabit team. Historical references: Reports on Robert Sun and educational psychology literature.