Okay, a weird topic I know but I saw a question asked in NewScientist querying whether the Domino’s Pizza claim of 1.8 billion combinations is possible. Here is the answer I am submitting: If we have 4 options on the menu (ABCD) and choose 1 topping we have 4 unique combinations. If however we choose 2 toppings we have 6 unique combinations. As toppings in a different order are considered the same combination this means that when choosing the second topping we must choose from a sub-set of the entire menu. For example, when working out how many combinations...