7.8%。 The total winning rate of the preliminary contest of the national college students' mathematics competition is 7.8%. Judging from the historical data, the winning rate of the national college students' mathematics competition is not high. According to the data in 2022, the winning rate of the preliminary contest of the national college students' mathematics competition was 7.8%, while the winning rate of the final contest was 1.6%. This means that only a very small number of college students can win prizes in the national college mathematics competition.