Marie is buying an ice-cream sundae. there are 3 sizes of sundaes, 15 different ice-cream flavors, and 5 different toppings. how many ways can marie choose a sundae?

Since each size of sundae has 15 flavor choices, we can find the number of combinations by multiplying the size of sundaes with the different ice cream flavors. The same rule can be applied to the number of different toppings, so you can set up this equation:

Multiplying them out, you can see that there are 225 different combinations of sundaes