Donkeys years ago I drove upcountry to a car rally with 2 mates and a another bloke who was a mate of one of them.
One of my mates had one of those newfangled electronic calculator things. To pass the time (and to show off) he'd take rego numbers from passing cars, multiplying 3 figure digits by 3 figure digits.
About the 4th time he read the answer and the bloke I didn't know said straight away, 'no, that's wrong.' Turns out the calculator operator had entered a wrong digit.
The other bloke was doing the sums in his head faster than than you could punch the numbers into a calculator..........
