When a vacuum cleaner salesman persuades people to let him vacuum their living room for free, he is likely to increase his chances that he will make a sale. the salesman is using the:?

He is using the foot in the door technique. This is when you ask for small things and ingratiate yourself to a person in order to make way for larger things that the person would not ordinarily do. You ask for something small, and then that makes them more likely to give you something larger when you ask.