Sunday Maths: The Diagonal-Sum Mental Multiplication Method

This is a mental math technique to solve non-trivial integer multiplication I picked up from one of Arthur Benjamin's talks, and is widely used by other "mathemagicians" to solve large products.

It converts an n × n multiplication problem into a n² set of single digit multiplications, arithmetically identical to the "Lattice Method". However, instead of filling the lattice first and then summing each diagonal, this method calculates each sum as soon as possible - thus you only need to keep track of the bare minimum of working data and it becomes possible to do the problem entirely in your head.

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How to use a Unix PC as a Vocal Monitor

If you have a computer running on Linux or BSD, a microphone connected to it, and a desire not to spend $50 on a very small amplifier, you can use a one line shell script to listen to yourself sing instead.

Listening to yourself through a vocal monitor gives a better indication of the pitch and timbre of your voice than just listening to yourself, as the sound reaching your ears from your mouth is affected by resonating through your head, like listening to someone talk through a bone wall covered by a wet blanket. A monitor will therefore be a more accurate reproduction of what you sound like to everyone else than "directly" listening to your own voice.

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First Post - About the Site and Author

About this Site

This site is intended to be a blog of short updates of variable frquency, so I can post assorted notes and rants and links that interest me - in contrast to my older site which is more of an old-school (in several senses) website broken down by content categories and not the time that things were posted.

The two sites may be merged in the future - when I rebuilt my website in 2017 it was done partly with the intention of also putting a blog on the site, but I found mixing the two styles of content delivery put me off. With the site mostly large monolithic projects it discouraged me from making small incremental updates, posting offtopic things or starting new sections.

Starting this blog as a clean slate should help me get past that block, and be comfortable posting little things.

Why "Readable by All"?

It's a pun on the domain name and this being a public site.

Why "drwxr-xr-x"?

If you're using a Unix-like operating system you probably get this already, and if you're not, it's probably not worth explaining.

About the Author

I'm a former academic/researcher/teacher/developer, now effectively unable to work and now retired permanently on disability pension.

In the time when I'm able to have at least the upper half of my body in the vertical position, I play a few intruments and many different games, and try to cook food that won't aggravate my medical issues.


I know this may be asked sometime later when I start posting science content:

Bachelor of Science (Honours First Class)
Victoria University, Melbourne, 2015
Bachelor of Computer Science
RMIT University, Melbourne, 2011
Bachelor of Engineering
RMIT University, Melbourne, 2011

Note: In Australia, Honours is usually a separate, short degree with at least 50% research content done just after undergraduate studies, a sort of mini-research-postgrad. It's not usually awarded alongside your undergraduate degree(s) or for getting a high mark in your undergraduate, which seems to be more common in the UK or US.

Research I've Written

All my formal/official forensics research work done at Victoria University or RMIT University is covered at

Software I've Written

See the software page on my website or my Github page.