A hot dog consists of a sausage in a bun with sauce. Onion, tomato, pineapple and cheese are available as extras. How many different types of hot dog can be made?
This answer is totally wrong.
Using only one extra you get 4 different hot dogs.
Using two extras you get 4C2 = 6 different hot dogs.
Continue in this way and then add them all up.
I assume a hot dog with no extras counts as a seperate type ....?