While teaching in Singapore in 1960 Guy met the Hungarian mathematician Paul Erdős. Erdős was famous for posing and fixing difficult mathematical problems and shared a number of of them with Man. Guy was intrigued by unsolved issues and wrote two books devoted to them. Many number theorists received their begin trying to solve issues from Guy’s book Unsolved issues in quantity idea. In a career that spans eight a long time he wrote or co-authored greater than a dozen books and collaborated with some of a very powerful mathematicians of the twentieth century. Paul Erdős, John H. Conway, Donald