How many people can be fed?

When sizes of pizzas are quoted in inches, the number quoted is the diameter of the pizza. A restaurant advertises an 8-http://session.masteringphysics.com/...B%5Crm+inch%7D "personal pizza." If this 8-http://session.masteringphysics.com/...B%5Crm+inch%7D pizza is the right size for one person, how many people can be fed by a large 16-http://session.masteringphysics.com/...B%5Crm+inch%7D pizza?

This is suppose to be simple, but i dont know why i am having trouble.(Crying)