4/ 12× 3/11× 2/10 analysis: the first lady is 4/12. The second one is 3/ 1 1, because the girl student of 1 1 has been drawn, so only one girl can be selected from 1 1, and the probability is 3/1. Similarly, the third one is 2/ 10. According to the principle of step counting, three probabilities are multiplied, and the probability is 1/55. You can ask me if you don't understand. I hope it helps.