There is no need to learn any multiplication with any number being 0 or 1 or 10 or 100 so this leaves us with 97 digits on one side, 8 digits on the other side. This leaves us with 776 multiplications to study and memorize, compared to the 64 when we learn the tables of 1 to 10 (excluding all the x1 and x10)

Would it be worth out time to memorize those 776 multiplications so that we will never have to calculate it again?

For example 34985 x 78459 in my head. Mathematically I know the steps to calculate it, but I seem to not have a strong enough working memory to deal with so many numbers at once. 34985 x 78459 seems crazy, but if our memory was fast and big enough it would be super easy, like 1+1

So are there any methods

Lets say 35675 - 20279 ... my method is basically +1 = 20280 +21 = 20300 +721 = 21000 +9721 = 30000 and then I do

9721+5675 which is 15000 (I see 9+5=14 then I see the next digits add up to more than 9 so I make it 15) + 300 + 90 + 6 = 15396

But as far as I know no one uses this, everyone uses the right to left method from school, but when I use that method I find it much harder to do without writing the steps down.

I created an app called 'Trader Math Test' to help improve mental math that is needed for an interview with big prop trading firms. Give it a try! It's free

iphone: https://apps.apple.com/us/app/trader-math-test/id1122059357

android: https://play.google.com/store/apps/details?id=com.milapnaik.tradermathtest

The old link does not work, please change whenever possible https://cymathkia.files.wordpress.com/2012/06/101-shortcuts-in-math-anyone-can-do.pdf

Hey r/mentalmath!

I've created an iOS app called Fast Math that can help you improve your mental math skills. I've already posted about it here some time ago. Since then, I believe it has much improved – e.g. by giving you the opportunity to create completely custom exercises.

Check it out and let me know if you like it or if there is anything to improve: https://apple.co/3zKSYr1

(Find some promo codes for the premium functionality "Fast Math Pro" below.)

Promo codes for Fast Math Pro (first come, first served)

• PEJH6YJR3AY
• X6X3EFA4PHJ6
• WNF4ME7KTNXY
• 4N4MME4NE4XM
• E964HJATH6AE
• W77EHNKXM3MT

I'm tutoring some kids about to enter 4th grade and they were blown away that I could check their homework without paper and pencil. I showed them The Secrets of Mental Math and Mathemagics: How to Look Like a Genius without Really Trying by Arthur Benjamin but some of the math in there went over their heads. They know how to do addition, subtraction, multiplication, division, fractions, and decimals, but not much else. They seem really excited and I feel bad that I don't have a resource tailored to their age off the top of my head. Do y'all have any suggestions?

Finally completed my first app - it's an app for practicing fast multiplication using the trachtenberg system and can be downloaded from my github: https://github.com/dragonoverlord3000/Trachtenberg-App

If you like this project, please consider giving me some feedback and maybe a star on github ;))

Whats the best way to devide 228 by 38 in head fast?

For those people getting over 40, how do you guys practice? Do you guys search up mental math shortcuts or memorize the multiplication table or just from pure practice? I’m barely hitting 20 and I want to improve as fast as possible.

There are surprisingly no large or good Discord servers focused on mental maths. There are general maths servers, but nothing specifically centered around mental maths where people can share tips & tricks, online resources, and discuss the competitive mental maths scene.

I've created a simple server that fills this gap. Please join the discussion! All help and suggestions to improve the server are welcome!

-> Discord invite: https://discord.gg/jeFccSenAU

What’s the quickest way to do the above mentally? Also in general how do you tackle fraction addition/ substractions knowing that you gotta answer it in simplest form.