Let the total number of questions in the test be N and the marks for each question be M. The candidate attempted 12 questions, all correctly, so the total marks obtained are 12*M. This score represents 60% of the total marks of the test. The total marks of the test are N*M. Therefore, 12*M = 0.60 * (N*M). Simplifying this equation by dividing both sides by M (since M cannot be zero), we get 12 = 0.60 * N. Solving for N, we find N = 12 / 0.60 = 12 / (6/10) = 12 * (10/6) = 20.