Chinese Mathematical Olympiad

The Chinese Mathematical Olympiad (中国数学奥林匹克) is an annual invitational mathematical competition for high school students in China organized by the Chinese Mathematical Society. Its participants are teams of high school students from every province of mainland China, as well as guest teams from the two special administrative regions Hong Kong and Macau, and also from Russia and Singapore. It is part of the selection process for the Chinese team to the International Mathematical Olympiad.

Eligibility
To take part in the Chinese Mathematical Olympiad, high school students have to attain top positions in their own provinces in the National High School Mathematics Competition, which is held on the second Sunday of September each year. Provincial mathematics societies often hold preliminary tests to pre-select students for the National High School Mathematics Competition, although these tests do not constitute a part of the official IMO team selection process. Then, based on the results, each province is allocated a quota to enter the Chinese Mathematical Olympiad. In early editions, the quota was usually 3 to 5 for a province, but could go up to 15 for strong provinces such as Beijing. The quotas have since increased significantly, for instance the quotas for the 2023 CMO ranged from 6 to 26, totalling about 550. Also invited to the CMO are past national training squad members who are still in high schools, and the top 15 contestants in the China Girls Mathematical Olympiad.

Format
The Chinese Mathematical Olympiad follows the same format as the IMO. Two papers are set, each with 3 problems. The examination is held on two consecutive mornings, and contestants have 4 hours and 30 minutes each day to work on the 3 problems. The Chinese Mathematical Olympiad is graded in 3-point increments, so that each problem is worth 21 points, making the total score 126, triple that of the IMO.

Awards
The Chinese Mathematical Olympiad has first, second and third class awards. There is also an award for the best team called "Chern Shiing-Shen Cup".

National training squad
Currently, about 60 highest-scoring contestants amongst the first class award winners are invited to the national training squad, who will go through a training to select the IMO team. Until 2016, the training consisted of a single phase with several regular tests and a team selection test, which was in the format of the IMO. The IMO team was selected based on the final result, of which both the regular tests and the team selection test were worth 50%. Since 2017, the training has been split into two phases. In each phase of training that lasts for about 8 to 9 days, two team selection tests, each of the same format as the IMO, are conducted. In the first phase, 15 top scoring members are selected to the next phase, and at the end of the second phase, the six IMO team members are selected based on the total points of the four team selection tests. Members of the national training squad have guaranteed admission to any universities in China without sitting the Gaokao examination.

History
China received the first invitation to the IMO from Romania in 1978, which was the first time its mathematics community learnt of it. Since having been invited to the 1981 IMO from the United States, the Chinese Mathematical Society had been preparing to participate in the IMO while waiting for approval from the China Association for Science and Technology. Upon hearing that the representatives of China had been asked again to join the IMO in a UNESCO meeting in Paris in April 1985, the leadership decided to join at the end of April, just two months before the IMO. The Chinese Mathematical Society then selected two students from Beijing and Shanghai using that year's American Invitational Mathematics Examination paper, and sent them to the 1985 IMO as a trial. At the 50th anniversary meeting of the society in December 1985, it was decided that a competition was to be held in January 1986 to select students to the IMO. It was called the National High School Mathematics Winter Camp. From 81 contestants, 21 were selected to the training squad, from which 6 were selected to the IMO Chinese team. In the 1990 Winter Camp, the "Chern Shiing-Shen Cup" was created with the donation by renowned mathematician Shiing-Shen Chern. After hosting the IMO in Beijing in 1990, the Winter Camp was named the Chinese Mathematical Olympiad in 1991.

The Chinese Mathematical Olympiad used to be held in universities; while since 2002, except in 2004, it has been held in high schools. The Chinese Mathematical Olympiad has been moved from January to November or December of the previous year since 2013, so there were two editions of the CMO in 2013, one in January and one in December.