i'm terrible at math. trust me, you math experts will see why after reading my question.

i have an object that is 300px in height. i need to calculate the percentage of that height where 90% = 300px (or the full height), 45% = 150px, 0% = 0px. so essentially, if i ask for 45% of the object's height, it will return 150px, or if i ask for 32% of the object's height, it will return __?

i believe this is really basic math, so i apologize in advance.