ale_sicheri
A college cafeteria offers three sizes of pizza - small, medium, or large. With a small pizza, up to one topping is included without additional charge; for a medium or large, up to two different toppings are included without additional charge. The cafeteria offers two meat toppings - pepperoni and sausage. If the cafeteria offers N other toppings, then how many ways can someone order a pizza - choosing a size and up to the maximum number of toppings - without having to pay extra? Assume that double toppings are not an option.
A. 3/2N^2 + 9/2N + 3
B. 2N^2 + 7N + 6
C. N^2 + 7/2N + 3
D. 3N^2 + 9N + 6
E. N^2 + 4N + 4
Please let me know your reasoning as I cannot find a proper answer to this question anywhere.
Thanks
There are two possible scenario in which small pizza can be ordered.
1) When 1 topping is selected from meat sausage
2) When 1 topping is selected from other N toppings
2c1+ Nc1 = 2+N
Now, let's look at the way to order small or large pizza
1) when both the toppings are ordered from meat
2) When 1 topping is ordered from meat, and other from remaining N
3) When both the toppings are ordered from N other toppings
Also, since both medium, and large pizza offers two toppings, and the number of ways to order the pizza is identical hence we have to multiple the above mentioned scenarios with 2.
(2c2)*2 + (Nc1*2c1)*2 + (Nc2)*2
=2+4N+N(N-1)
=2+3N+N^2
Thus total number of ways to order pizza = N^2+3N+2+N+2 = N^2+4N+4
IMO E