Quick - where's the calculator?

A recent poll has found that a fifth of adults struggle with basic maths calculations - I don't find that so surprising, but what did amaze me was that when it came to times tables, the one that caught most people out was the 11-times table.  Surely this must be the second easiest to deal with - the 10-times being the easiest - because, at least up to 9 it simply involves repeating the basic number twice.  So 7 elevens are 77, 4 elevens are 44 and so on.  Bit trickier with 10, 11 an 12, but surely one of the simplest?