You would often wonder what goes on in the minds or lives of the people who set examination questions.

Take the following question, which Leaving Cert maths students (ordinary level) had to face just the other day: a car journey of 559 kilometres took six hours and 30 minutes. Calculate the average speed, in km/hr, for the journey.

As you sit biting your pencil, all kinds of other questions quite naturally spring to mind. What kind of people would make a trip of 559 kilometres, which is over 370 miles? Is it some crowd in Antrim going to West Cork for the holidays? Was the trip made before or after the opening of the Kinnegad bypass? Did they stop for a bite to eat, and maybe a glass of Guinness, or is the driver one of those determined people who won't "break" the journey under any circumstances? At what point did the child in the back first ask "are we there yet?" If they're from Antrim, what foot do they kick with?

After an agony of calculation, you conclude that this suspect crowd, perhaps in a two-year-old Nissan Primera, have arrived at their holiday home a mile from Schull, absolutely wrecked, at 10.55 on a Saturday night, having averaged 86 kilometres per hour. With the car emptied just 20 minutes later, the da does an even more impressive average on his own as he makes a mad dash into town for last orders in the Bunratty Inn.

A speed of 86 kph is a pretty good average for a long journey. In fact it's not far off 60 miles an hour, which just happens to be the national speed limit on this side of the border. So other questions naturally arise. Anyone who drives down the country at all, and has even a modest regard for the laws of the land, know how hard it is to keep up a half-decent average speed. You won't get from Dublin to Galway for example in much under three hours, and that's only about 135 miles, so you're only averaging 45 mph. If you were to stop off for a quick one at Curley's in Kilreekil, which is by far the best part of any trip to Galway, you would probably cut your average speed to 40 mph.

We have to conclude then that the Antrim crowd, in order to maintain their 86 kph average speed, have really been putting the boot down when out on the open road, and not stuck between Enfield and Kinnegad, or in so-called traffic-calming areas, or 30 mph zones. As for the bits of motorway on which you can legally do 70 mph, these will not make much difference to the final outcome.

The way it is, then, those bloody out-of-staters, almost definitely Protestants, must have been doing the ton, if not more, on our national roads, to keep up a very suspect average speed the way they did. The cheek of them, and them not even paying road tax in the Republic.

But say some decent Dublin couple, with the son coming up to the Leaving Cert, takes a look in all innocence at the exam question. Young William, now gone 17, does his best, but maths is not his strongest subject - hard to say what is - and the parents are keen to help in any way they can.

What do they do? They decide to take a good long trip in the car with William, to give him an idea about distances and average speed and miles per hour and kilometres per hour and amount of petrol consumed. William isn't that keen. In fact he can't believe his parents could be so obtuse. He's going to a party on Friday, and another on Saturday. He has not the slightest interest in miles per hour or a dull weekend in Cork with his boring parents.

What's more, the Leaving Cert is a year away, which for William and his friends is a millennium.

Joe and Maureen, William's parents, finally buy him off with the promise of £100 in cash, and the three get in the car on a wet Friday morning in May. They are travelling from their home in Dublin to a B&B in Castletownshend.

The trip is a disaster. They have a puncture in Crumlin. William has a mild asthma attack in Kildare. Some gobshite flashing by in a Mercedes 200 clips the wing mirror of their nearly-new Corolla just outside Cashel. Going through the new Jack Lynch tunnel in Cork, Maureen is overcome by "darkness panic", and they have to reverse 300 metres and take the old ring road instead.

When they get to Castletownshend at 11.45 p.m. they discover they are staying for the weekend in a 19th-century British Protestant village, transposed to West Cork. The Nissan Primera crowd from Antrim, over from Schull for the evening, are in Annie's bar, singing The Sash.

Joe and Maureen's average speed for the trip of over 200 miles is 23.7 miles per hour, and William is not interested.