Gathering a minyan

Q: My husband passed away and we were at the cemetery. We only had nine men and my son did not say Kaddish. I told him that there were many people at the cemetery and there was no obligation to have them together and there was a minyan. What is Ha-Rav's opinion?
A: You are right and he is right. He is right: you need ten men. If the tenth person does not know what you are doing and is not joining you then he is not considered part of the minyan. But you are right that if there is a tenth man even though he is not right next to you, but he hears and answers the prayers and you signal to him, he is considered part of the minyan.