A pizza shop offers nine toppings. No topping is used more than once. What is the probability that the toppings on a pizza are pepperoni, onions, and mushrooms?
I think the way to solve it is 9C3 which equals 84. And the probability would be 0.012. But my friend is telling me its wrong because he did it by multiplying 1/9 x 1/8 x 1/7.
Can someone tell me who is right?

Question

A pizza shop offers nine toppings. No topping is used more than once. What is the probability that the toppings on a pizza are pepperoni, onions, and mushrooms?
I think the way to solve it is 9C3 which equals 84. And the probability would be 0.012. But my friend is telling me its wrong because he did it by multiplying 1/9 x 1/8 x 1/7.
Can someone tell me who is right?

anonymous · Answer

Be confident in your answers. :)

anonymous · Answer

There are 9-choose-0 ways =1 to have a pizza with zero toppings. 
9-choose-1 ways = 9 to have 1 topping 
9-choose-2 = 36 ways to have 2 toppings 
9-choose-3 = 84 ways to have 3 toppings 
Your answer is correct.