Fibonacci's 'Numbers': The Man Behind the Math 

"Though generations of schoolchildren have cursed arithmetic, the world was a much more inconvenient place without it. Before the advent of modern arithmetic in the 13th century, basic calculations required a physical abacus."

"But then came a young Italian mathematician named Leonardo da Pisa — no relation to da Vinci — who, in 1202, published a book titled Liber Abaci. That's Latin for 'Book of Calculation.'"