Water is being poured into a conical cup that is 12 cm tall.

a. When the water in the cup is 9 cm deep, what percentage of the cup is filled?

b. When the cup is 75% filled, how deep is the water?

I think it has to do with ratio, since it only gives you the height?

Along with the answer, can someone give me like a cheat sheet way of doing this, with either percentage,/ height,/ radius, etc.