*Liber Abaci* was not the first Western book to describe Arabic numerals, but by addressing tradesmen rather than academics it was the book that convinced the public of the superiority of the new system. The first section
introduces the Arabic numberal system. The second section presents examples from commerce, such as conversions of currency and measurements, and calculations of profit and interest. The third section discusses a number of mathematical problems. One example, describing the growth of a population of rabbits, was the origin of the Fibonacci sequence for which the author is most famous today. The fourth section derives approximations, both numerical and geometrical, of irrational numbers such as square roots. The book also includes Euclidean geometric proofs and a study of simultaneous linear equations.