formulae aren't that obvious and easy to remember if you don't actually get WHY they are the way they are; as in why they have certain components in them. Remember the formula for the volume of a pyramid? 1/3(Area of base*height). It may be confusing why the 1/3 is there, but when you know the reason it becomes amazing and interesting the way everything in maths connects. Here's a video that shows why the 1/3 is there, check it out!
https://www.youtube.com/watch?v=BjbilpBaA-U