I find myself on this sunny morning seated at the food court deep in thought. I have my standard steaming large cappuccino sitting on the table inviting a sip from time to time — which is the only time I appear to exit momentarily from this trough of thoughtfulness.

I have commandeered a table and, on it, have spread my wares — laptop, printed paper, markers, pens.

Regulars, chomping on their hamburgers and crisply fried chicken wings nearby have, no doubt, noticed me here frequently.

Forty years ago — a man in his early 20s — I might have stopped to wonder what all the people who use a food court to eat, might think of me.

Forty years on, I am past that stage. I don’t see the people and, if indeed there are any glances directed my way, I don’t notice them.

I am simply lost in thought. Even as I write this, I am consumed by the tiny links in the subconscious that take our thinking from one point to the next — imitating a stream of consciousness. I realise I have just written the word ‘forty’ twice and I find that strange because I arrived at the table with numbers on my brain. And then, suddenly, my concentration is snapped.

A pair of voices from the table just ahead has managed to penetrate my thoughts. Two high school pupils are engaged in a discussion. In a world of sweeping generalisation one might expect these kids to be discussing movies or the latest songs, or their Facebook statuses. Only, these two don’t appear to be products of that generalised world.

They are discussing numbers. Mathematical numbers. A concept, in fact. How to quickly — in seconds — work out the square root of any number ending in 5!

Ordinarily, this type of conversation wouldn’t arrest my concentration but — with due reference to the subconscious link mentioned above — I find it incredibly coincidental that these kids and I sitting only a table away should all have numbers on the mind. I shall come to mine presently.

First to the two youngsters — who, if they heard me would scoff at the notion that I’d referred to them as such — but when you’re in your 60s, high school pupils are — despite the machismo, the chin hair and the packet of cigarettes in the top pocket — youngsters still, relatively speaking.

So I eavesdrop unabashedly and this is what I glean — most valuably, I have to add, because I managed to absolutely befuddle my prankster friend Barney 30 minutes later with my new found knowledge.

Anyhow ... “Take 35, for example,” says one of the pupils, “Now the last two digits in the answer are going to be 25 because 35 ends with a five. Now, take the number three in 35, double it you get six. Multiply this with six after adding one, which is seven. That gives you 42. So 4225 is the answer! Remember always to add the one.”

My coffee in the end became cold as I worked out the squares of several numbers ending with five, if only to test the proof. It worked. Absolutely. It nearly made me forget what I’d set out to research in the first place.

I’d been delving into the number 600! My personal milestone. With this column that’s the number I’ve reached after 12 continuous years. I’d been looking into what the world was doing in 600 AD before I was interrupted. Apparently, Chaturanga — the ancient Indian strategy game — the predecessor of shatranj or chess — was developed around this time.

In the end I realise, however, that numbers too are merely relative. It’s Barney, my mate, striding up to join me, who reminded me of that. Instead of a greeting the first thing he says is, “Always treat rock stars like ordinary people and ordinary people like rock stars.”

“Who said that?” I ask and he replied jokingly: “Mick Jagger. Probably 600 years ago!”

Now how did he know I was thinking 600, too?

Kevin Martin is a journalist based in Sydney, Australia.