How to “hold” number

Hi to everybody, I’m new member and I’ve just begun studying something about mental calculation and memorization techniques.
Can somebody advice me some techniques to hold number in my mind?
I made an example: if I have to do 11*54367, I can do it quickly in few seconds if I write it, but if I don’t do it I have some difficulties to remember the number 54367, or in general I have difficulties to remember “things in evolution”.
Which are the best techniques and the best ways of training the so called “mental-eyes”?
Thanks to everyone that answer this question.

Hi Luca, and welcome to the forums :slight_smile:

You’ve just described the biggest challenge in mental calculation, which is to cope with the limited working memory that the human mind has!

In scientific terms, we are talking about the working memory, and I’ve written here about the standard model for this (by Baddeley) and how it applies to mental calculation. I’ve also written about how we can calculate the limits of its size.

So how to deal with it? There are two main methods:

  • use efficient ways to represent numbers in your mind and practise. Usually this means doing it visually rather than using your inner voice.
  • use methods that require storing minimal information at once.

For your example of 11 x 54367, it’s hard for everyone because you need to remember the “54367” from the question as well as the partially-calculated answer. I would suggest using your inner voice to store the “54367”, and perform the calculation visually.


Thanks for the answer and the advices, I’m going to read the links.

About this:

Should the conversion fonetic-object useful? Or should it require too much “RAM-brain”?

First tip. practice, practice, practice.
Calculate daily.

I try to find things about numbers that have some meaning for me.
For me, the fact that I realize that 54 +36 = 90 helps in remembering the number.
Also 54+36+7 = 97 which is the highest two digit prime.
By playing with the numbers this way, I can retrace and find my original numbers if need be.

I have an auditory memory, so I need to say the numbers out loud in my head in order to remember them. I always try to see them as well. Find out whether you are auditory , visual or an kinaesthetic learner.
In any case, try to involve all your senses.

I usually don’t calculate with random numbers. When I calculate I have a reason, an interest, in the result of the calculation. For example if I want to calculate the mortgage on a I am thinking of buying, the inputs are the price of the house and the interest rates. These numbers are important for me and thus easy to remember.

If you are starting out, don’t start with five significant numbers. Try three. Round 54367 to 54400. I guestimate the answer first, so I don’t work with the zero’s and decimal points. In this case and for me, 54367 becomes 544 and I will set the decimal point or add zero’s later.

Try to do 11 * 544 in your head first.
Round 54367 to 54400. Realise you have added 33.

11 * 544 = 5984.

improve the calculation using the difference of 33. 11 * 33 = 363.
So take 598400 and subtract 363: 598037.

If you do it this way, you are working with four significant decimals, except for the last step.

You could do that.
54 can be LuRe, using standard Major System conversion.
36 = MaTCH
7 = hooK

I personally don’t use it, but but you can see Arthur Benjamin doing exactly this here: Faster than a calculator | Arthur Benjamin | TEDxOxford - YouTube and fast forward to 14 minutes.