Troy has already baked 17 cakes, and he can bake 3 cakes with each additional stick of butter he buys. How many additional sticks of butter does Troy need in order to bake a total of 47 cakes?

As stated in the problem, it takes 1 stick of butter to make 3 cakes. Troy already made 17 cakes but he want to make 47.

To find out how many more cakes he has to make, subtract 17 from 47, which is 30.

Troy needs to make another 30 cakes.

To find out how much butter he needs, divide 30 by 3, which is 10.

Troy needs another 10 sticks of butter.