What were Fibonacci's interests?

Fibonacci (real name 'Leonardo of Pisa') was obviously interested in mathematics, including arithmetic and algebra, but particularly mathematical theory. However his life history indicates a richer picture of the things that fascinated him. Although an Italian, born in Pisa, and doubtless used to using Roman Numerals ( I,II, III, IV, V, VI etc.), he became very interested in the Indian (Hindu-arabic) number system, a positional base10 numeral system (0,1,2,3,4,5,6 etc.) Knowledge of this 'art of numbers' pleased him above everything else. He evidently enjoyed travelling, even giving himself the nickname Bigollo, which may mean well-travelled! He also took an interest in Greek classical literature in the form of Latin translations that became available to him. After his travels he settled back in Pisa when he was 30 and enjoyed developing number theory and solutions to algebraic equations. He wrote an excellent book explaining the Roman 'finger-number' system (the basis for Roman Numerals), so evidently he enjoyed teaching, teaching others what he knew so well. In fact he advised the Pisa (City/Republic) authorities on matters of accountancy and on teaching the citizens, for which work he was awarded a state salary. Language itself had an allure to him, consequently he wrote about word puzzles/problems. In business matters he was intrigued with exchange rates, interest rates and profit margins. He had a keen interest in conversions of weights and measures and business bookkeeping. He even wrote a book solely about commercial arithmetic for traders and merchants, all this indicating an interest in business management, management accountancy and international trade. To assist in a practical way to the challenges facing surveyors he took an interest in geometry. Therefore his interests also included applied mathematics. He focus was always on practical problem solving, and was prepared to take the unprecedented view that a close approximation of an answer was better than no answer in equations where there was no clear integer or fractional answer. This approach is called rational approximation. It is interesting to note that the Arabic numeral system that Fibonacci took an interest in was only used by Arabic scientists and mathematicians, not by business people. He became aware of this fact and is noted for introducing the base-10 method into Arabic business, thus demonstrating his interest in helping all parties engaged in international trade to greater business efficiency. As one historian wrote, he can 'be credited with the introduction of scientific calculating techniques into general business practice.' * See also Related links below this box.