Doubt raise

Suppose I am attending an online class with a teacher and 49 other students. Many times teacher assume that we might know many things about the topic he is teaching, so he/she skips the portion. At the same time, some of us also think that maybe this is a simple topic that I have not studied So we do not interrupt the teacher. 

I am thinking about an option where we can raise a doubt silently. If the number of up hand for the doubt is more than x  % (X will be decided by the teacher) then there will be a notification to the teacher that "the topic he is teaching is not clear to x% student ) so that he can explain the topic in another way.