A pizza shop offers nin toppings. No topping is used more than once. What is the probability that the toppings are pepperoni, onions, olives, and mushrooms? Round your answer to the nearest thousandth.

Answer 1

Excel spreadsheets are very helpful for these kinds of problems.

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

Repeat for all 4 through 9 toppings.
Then sum all your answers. This is the denominator. The numerator is one.