... ☺ The best problems from around the world Cao Minh Quang 10023rd ASU 1989 problems 1. 7 boys each went to a shop 3 times. Each pair ... is < π/4. ☺ The best problems from around the world Cao Minh Quang 10224th ASU 1990 problems 1. Show that x4 > x - 1/2 for all real x. 2. ... at most 3n times. ☺ The best problems from around the world Cao Minh Quang 10425th ASU 1991 problems 1. Find all integers a, b, c, d such that ab - 2cd...