It might be a Douglas Adams tribute, but it also might be that large numbers of children at that age haven't yet grasped place value and don't realize that 20, 30, 40 and so on are in fact ways to represent 2 tens, 3 tens, 4 tens, and so on, and "forty three" is actually pretty confusing to say, since it has a word that sounds very similar to "four" followed by the word "three", a sequence out of their usual counting order (and this is the first time this kind of juxtaposition occurs in the English counting sequence.)
