> I don't understand how that math could work. Assuming random assignment, the probability that a given computer is given to a one of those students is identical from year to year.

That's fair. I guess, it's more accurate to say that you'd expect a number of laptops equal to the size of the initial tranche to be destroyed after the first 5 years.

Although if I was running IT, it'd definitely keep track of the "destructive" students and issue them the oldest equipment, in which case, we'd be back to something closer to my original statement.