世界数学奥林匹克经典：概率与期望

　　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.

　　作者简介单墫，我国著名数学家、数学教育家。1943年11月生，1964年扬州师范学院数学系毕业，1983年在中国科学技术大学获理学博士学位，师从王元院士，为我国首批获得理科博士学位的18人之一。博士毕业后在南京师范大学任教，1991年被评为全国优秀教师并享受国务院特殊津贴，1992年被授予有突出贡献的中青年专家称号。曾任南京数学学会理事长，南京师范大学数学系主任，中国数学奥林匹克委员会委员、教练组组长，国家教育司门理科试验班专家组组长。单墫教授在数学领域的初等数论、解析数论和组合数学研究方面取得了一些国际先进水平的成果。他还在数学普及与数学竞赛方面，倾注了大量的时间和精力。作为领队和主教练，多次率领中国国家队参加国际数学奥林匹克（IMO）均获全球总分，为我国数学教育事业作出重大贡献。