Question

Izzi's Pizza wants to offer at least 15 options for ordering 2 vegetable topping pizzas. What is the minimum

number of vegetable topping choices they need to offer?

Answer 1

Answer: 6 vegetable topping choices.

Explanation:

If we have two toppings out of X, the number of possible combinations is:

`c = (x!)/((x-2)!2!)`

and we want that c ≥ 15

We can do it by brute force:

Let's select x = 5 for example:

`c(5) = (5!)/(3!*2!) = (5*4)/(2*1) = 5*2 = 10`

So with 5 vegetable toppings we have not enough, let's see with 6.

`c(6) = (6!)/(4!*2!) = (6*5)/(2) = 3*5 = 15`

So with 6 options we have exactly 15 different combinations, the correct answer is 6.