(1) The number of participants in this competition is 3+6+8+2+1= 20;

(2) The winning rate of students in this class is11÷ 20 = 55%;

(3) The passing score is 150×60%=90.

The number of qualified participants is 8+2+ 1= 1 1.

So the answer is 20,55%, 1 1.