世界數學奧林匹克經典：概率與期望

　　Probability theory is an important branch of mathematics， with wide applications in many fields. It is not only a required course for students of science and technology at universities， but also has entered into Chinese high school textbooks now.This little book will， in an interesting problem-solving way， explain what probability theory is： its concepts， methods and meanings; particularly， two important concepts-probability and mathematical expectation （briefly expectation）-are emphasized. It consists of 65 problems， appended by 107 exercises and their answers.As an extracurricular book providing supplement materials to and advanced knowledge beyond high school textbooks， its aim is to stimulate study interests of students and broaden their knowledge horizons. Some problems were given a little deeper treatment， which can be used as topics for explorative study; and they can also be skipped temporarily if a reader feels difficult to understand them at the beginning.It is presupposed that our readers possess a knowledge of permutations and combinations， and it would be better if they have already learned basic probability theory from their textbooks. However， in order to avoid repetition， we mention as little as possible the contents of textbooks.It is a random event that this little book reaches you. I do not know how much the probability that this event occurs is. However， it is my expectation that this book could reach you， which means that you have a special affinity with it.

　　作者簡介單墫，我國著名數學家、數學教育家。1943年11月生，1964年揚州師范學院數學系畢業(yè)，1983年在中國科學技術大學獲理學博士學位，師從王元院士，為我國首批獲得理科博士學位的18人之一。博士畢業(yè)后在南京師范大學任教，1991年被評為全國優(yōu)秀教師并享受國務院特殊津貼，1992年被授予有突出貢獻的中青年專家稱號。曾任南京數學學會理事長，南京師范大學數學系主任，中國數學奧林匹克委員會委員、教練組組長，國家教育司門理科試驗班專家組組長。單墫教授在數學領域的初等數論、解析數論和組合數學研究方面取得了一些國際先進水平的成果。他還在數學普及與數學競賽方面，傾注了大量的時間和精力。作為領隊和主教練，多次率領中國國家隊參加國際數學奧林匹克（IMO）均獲全球總分，為我國數學教育事業(yè)作出重大貢獻。