In the preface to his book The Road to Reality, Roger Penrose tells the story of a friend whom he used to tutor in mathematics and who, faced with simple fractions, was completely unable to cancel them because she kept picturing the nominator and the denominator as ‘two separate things’.21 This fact is also relevant to financial education and to the protection of banks’ customers.
As I have said on other occasions, the rules that provide for transparency on (various definitions of) annual percentage rates of interest are not particularly useful to those consumers – a non-negligible share, according to surveys – who are not fully familiar with the concept of interest rates itself. 5  What can we do?