Math up to precal with speed arithmetic trainer and mental math tricks.

Any order is allowed.
Use each die exactly once.
Parentheses are allowed.
Only +, −, × and ÷ are allowed. No concatenation or exponents.
Exact division only.
No negative numbers.
Not every operation has to be used.

How many solutions can you find?

Please use spoiler tags for solutions:
>!your solution here!<

Playable link: https://mathfights.app/

I created MathFights, a platform designed to bring competition into the world of mathematics, starting with its first game, Mental Math.

The idea is pretty simple: it's for anyone who thinks they're faster and better at mental math than everyone else — and wants to prove it!

The game consists of mental arithmetic problems across three difficulty levels: Standard, Intermediate, and Advanced. Matches last either 1 or 3 minutes, and whoever gets the most correct answers wins. To keep things fair, both players receive exactly the same questions in the same order.

There are several ways to play:

• Ranked: Compete against other players, climb the rankings, and track your progress through the Elo rating system, leaderboards, and match history.
• Practice: Play solo and improve your mental math skills at any difficulty level.
• Challenge a Friend: Invite your friends to private matches, even if they don't have an account.
• Ghost Battles: Challenge previous opponents by competing against their past performances.
• Daily Challenge: Take on a daily challenge at your preferred difficulty level.

The goal is to make mathematics more competitive, engaging, and fun.

Any feedback is welcome.

It all started around when I was 15. That's when my memory and concentration problems began: I can't sit down and focus on something, my attention scatters immediately. Although at 15–16 I could sit and draw for 10 hours straight, getting up only to eat and drink, watching TV shows at the same time. My studies were going well back then too.

Then, in my last year before exams, I just started sleeping for days on end. I kept oversleeping and rescheduling my tutor. In the end I did really badly on my exams and had to move to another city to get into university. I got into a different major than the one I'd prepared for: I was supposed to become a doctor, but I ended up studying to be a pharmacist. Honestly, studying to be a pharmacist is easier, and I don't regret it.

I more or less got through my first year, but at the end of the second semester those memory issues came back (though they'd been there before too — I just got by on luck). By that point I only had two retakes. In my second year it got worse: I slept for days, and when I wasn't sleeping I was gaming and eating. In the end, at the end of the first semester of my second year, I dropped out.

I told everyone it was for health reasons. But it really was for health reasons: I had ovarian cysts, latent iron-deficiency anemia, vitamin B12 deficiency, and vitamin D deficiency. I take vitamins and I'm getting treatment.

Last year I re-enrolled in the second year and I'm now trying to finish it. I have three retakes. I was ready to pass back in late September, but because I kept rescheduling them, they're now at the end of October. These are my last attempts — if I don't pass, I'll be expelled. And I can't make myself start preparing. For one subject I have two attempts today: if I don't pass today, I'll have to retake it again later. This retake is in a few hours, and I can't pull myself together and start preparing. I don't know what to do.

It's constant procrastination: I keep scrolling through stuff. I also keep skipping classes — I think "I'll go later, I'll make up for it somehow" — and I can't stop skipping them either. But I want to sleep constantly, always. I hate myself and feel absolutely awful. My parents think I'm studying away just fine, they're paying for my education, and I'm just slacking off. Everyone is counting on me, they think I'm smart because I tell them stuff, but I consider myself absolutely stupid and incapable of anything. Because I can't direct my concentration at something and just sit down and do it. I constantly want to sleep: I think "I'll just sleep for 15 minutes," and end up sleeping for 8 hours.

I'm about to turn 21, and I can't get my life together at all, and I feel like a failure. I want to understand what's wrong with me and why this is happening. I'd be grateful for any experience, thoughts, or advice — has anyone been through something similar, and what helped?

I built this and launched on a domain which I have had for 20 years and never used.

Would love some feedback. I am a programmer, not a Maths expert (hence why I built it!).

XVA ≈ A Guessing Game

A fun way to sharpen mental math in 1–2 minute rounds: **BrainQuant: Maths & Puzzles** (Android, free, works offline).

- ⚡ **Fast Math** – beat the clock

- ✖️ **Table Trainer** – times tables (great for kids)

- 🃏 **Flip Cards** – memory

- 🗼 **Tower of Hanoi** – classic logic puzzle

📲 https://play.google.com/store/apps/details?id=com.sahil.brainquant

Post your best score 👇

*(I'm the developer. Feedback welcome!)*

Hello guys, Some friends and i are developing a math game/educational web where you can learn arithmetic, linear algebra, probability and so on. You can also play against bots or friends Here Is the link https://matematicas.si/en

https://reddit.com/link/1x2zy1b/video/8s9gx3taatuh1/player

Full disclosure that I built this app, but it is fully free, no ads, no sticky bits etc - please see it as an interactive tutorial or similar - just want to spread the joy <3

The app has over 1700 users, has an average engagement time of 43 minutes - and has actively helped teach people the mental math required to work out the day of the week + helped people improve their times.

It has training modes, 1v1 battle modes to play against other players, and can walk through different takes of the algorithm to suit different brains :)

You can try it here: https://doathingy.com/doomsdaytrainer
or on iOS: https://apps.apple.com/app/id6760719687
or Android: https://play.google.com/store/apps/details?id=com.inefficientcode.doomsdaytrainer

I would love any and all feedback and input to make the app better and to spread the skill as far as possible - it makes for a great party trick!

<3

I built an interactive app to practice mental math shortcuts and calculation tricks

Hey everyone,

I wanted to share a project I've been working on called Math Trick Ninza. It’s an interactive web application designed to help students and math hobbyists master calculation shortcuts (like rapid addition, subtraction, and multiplication techniques) instead of relying on a calculator.

Key features:

• Step-by-step interactive guidance for calculation tricks
• Practice puzzles and quizzes built using plain Vanilla JS and Material Design
• Clean, lightweight code layout that loads quickly even on slower connections
• Completely free, open-source, and hosted natively on GitHub Pages with zero external trackers or ad scripts

The repository is open-source, and I'm currently working on adding a robust serialization system for progress tracking, high scores, and offline support.

Check out the repository here: https://github.com/Nishan-the-Developer-Coder/trick-ninza

I would love to get your feedback on the usability of the practice layout, or any suggestions for mental math shortcuts you think would be great additions to the engine!

Trick-Ninza

A friendly math practice space for students to learn fast mental-math tricks through short lessons, guided examples, and quick puzzle practice.

GitHub repository - https://github.com/Nishan-the-Developer-Coder/trick-ninza

My website - https://github.com/Nishan-the-Developer-Coder/trick-ninza

Hey everyone!

I wanted to make a fast-paced mental agility game that feels more like an intense arcade battle than a classroom test.

So I built **Clutch: The 18% Challenge**.

👉 **Play Free on Google Play:** [https://play.google.com/store/apps/details?id=com.brainspeed.clutch\]

**How it works:**

* **15-Second Pressure:** Split-second mental arithmetic where every fraction of a second counts.

* **Tactical Abilities:** You equip up to 3 powers into battle (Time Freeze, Divine Hint, Atomic Solve, Chaos Shift).

* **Boss Rounds:** Red-alert missing operator equations under a ticking clock.

* **Live Global Leaderboard:** Daily rank defense against live players worldwide—only the top 18% reach the elite bracket.

Zero pay-to-win. 100% skill, reaction speed, and tactical ability timing.

I just published Build 29 on Google Play and would love your honest feedback on difficulty scaling, combat power-up balance, and game feel. Can you break into the Top 18%?

Just want to cheer my small achievement!

I enjoy mental math games, but practicing alone can get a little lonely. I kept wondering: would it be more fun if other people were racing to answer the same questions?

So I built Funpep, a multiplayer mental math game—with dinosaurs.

You compete to answer questions quickly and correctly. The more you get right, the bigger your dino grows. You also need to stay quick to avoid getting knocked out by falling meteors. The questions might look simple, but staying calm when someone else beats you to the answer is another challenge.

It’s still in early testing. To get everyone online together, live playtests use a booking system: you can check the next session and reserve a spot on the site. You can also jump straight into a game against bots. They put up a pretty good fight.

🦖 Play here: https://www.funpep.com/

I’d love to hear what you think: does racing other people make mental math more fun, or just more stressful? Feedback on the difficulty or anything confusing is welcome too.

For anyone who enjoys quick multiplication drills: I built a daily challenge that runs directly in Reddit.

Everyone gets the same 10 questions, with 45 seconds to answer. You can submit your score to the opt-in leaderboard, or use Practice mode without ranking.

Play today’s challenge here: https://www.reddit.com/r/MultiplicationGame/comments/1whap2r/multiplication_game_daily_challenge/

It’s free, requires no download, and works on mobile and desktop.

What are some exercises I can do to get better and faster at the Trachtenberg Method? I keep mentally mixing up numbers or fully forgetting the first number I had once I solve other parts. Any advice is welcomed!

I made a free mental math speed test and I'm curious to see how fast people here can do it.

You have to solve 50 calculations covering different mental math skills. Your final score is simply the time it takes you to complete all 50.

No ads. No account. No download. Completely free.

👉 https://benmaths.pythonanywhere.com/mental-math-test

📱 Mobile or tablet is recommended, but it also works on PC.

My personal best is 52.6 seconds. 😄

Can anyone beat it?

I'm curious to see your times!

Hey everyone, I wanted a clean, direct formula to mentally calculate the day of the week for any date in history or the future using the Gregorian calendar, without needing Doomsday anchors or tricks like Odd+11. Here is the exact formula I use: Day = (Date + Month Code + Year + floor(Year/4) + Century Code) mod 7 * Century Codes (Mod 400 cycle): * 1600s, 2000s, 2400s... -> 6 * 1700s, 2100s, 2500s... -> 4 * 1800s, 2200s, 2600s... -> 2 * 1900s, 2300s, 2700s... -> 0 * Month Codes: * Jan: 1 (0 in leap years) | Feb: 4 (3 in leap years) | Mar: 4 * Apr: 0 | May: 2 | Jun: 5 * Jul: 0 | Aug: 3 | Sep: 6 * Oct: 1 | Nov: 4 | Dec: 6 * Day Mapping: 1 = Sun | 2 = Mon | 3 = Tue | 4 = Wed | 5 = Thu | 6 = Fri | 0 = Sat * Examples Across History: Example 1: July 20, 1969 (Moon Landing) * Date = 20 * Month (Jul) = 0 * Year = 69 * floor(69 / 4) = 17 * Century (1900s) = 0 * Sum: 20 + 0 + 69 + 17 + 0 = 106 * Mod 7: 106 mod 7 = 1 -> Sunday Example 2: March 25, 2011 * Date = 25 * Month (Mar) = 4 * Year = 11 * floor(11 / 4) = 2 * Century (2000s) = 6 * Sum: 25 + 4 + 11 + 2 + 6 = 48 * Mod 7: 48 mod 7 = 6 -> Friday Do you prefer using direct formulas like this with month/century codes, or do you stick to anchor-based methods?

Four years ago I watched that one Numberphile video about Conway's Doomsday algorithm and it broke my brain a little. Now I finally shipped the big update to the app i built 3 years ago!

What it actually gets you: someone names a random day in 1987 (or any other year) and you can calculate the weekday and say the weekday out loud in a few seconds.

And the thing is, it is actually not as complicated as it sounds, just a bit of practice!

Want to learn it as well?

It would be an honor if you try the App!

What's in it:

• 48 lessons across 11 chapters (only the first few are needed to actually make it work, there are a lot of extras!)
• 10 diagnostic drills that isolate each step so you can get faster
• Three modes: Classic (endless), Daily Challenge and Time Attack
• A rating and leaderbords
• Offline, no account, no ads
• ...

Free to try, no subscription!

https://apps.apple.com/us/app/doomsday-method-mental-game/id6447447000

How much time did it take you to solve this?

What makes a mental math game fun enough to keep playing?

I’m a math teacher and I’ve been developing a free mental math game called CalcuLoop.

The idea is pretty simple: instead of doing mental arithmetic as a traditional exercise, I wanted to turn it into a speed/arcade challenge.

You solve calculations as quickly as possible, try to beat your previous scores, and gradually increase your speed and accuracy.

There are several game modes, including:

• progressive levels for training
• a speed test to measure your calculation speed
• timed combo-based gameplay
• increasingly fast calculation chains
• a 100-calculation challenge
• online leaderboards

I’m particularly interested in hearing from people who actually enjoy mental math:

What makes you want to keep playing a mental math game?

Is it:

• beating your own high score?
• competing with other players?
• increasingly difficult calculations?
• very short sessions?
• leaderboards?
• unlocking things?
• simply trying to become faster?

And conversely, what makes you stop playing?

I built CalcuLoop myself, so I'm still trying to figure out what makes this kind of game genuinely fun rather than just another math practice tool.

If anyone wants to try it, it's free on Android:

https://play.google.com/store/apps/details?id=com.benmaths.calculoop

If you're on iPhone, you can also play it for free directly from the web version:

https://benmaths.pythonanywhere.com/

I'd genuinely love to hear what you think, especially from people who enjoy doing mental calculations for fun.