Think of it as your adding 3 plus 3 plus 3. 3 plus 3 is 6 then when you add it one more time its 9 meaning you added 3 plus 3 three times which is Nine
Notice how the 3 is put into fraction form 3/1. This allows you to multiply numerators for the product numerator and denominators for the product denominator.
Okay, so we already have the volume equation for a cylinder here.
Since we need to find the height(h), we need to basically isolate it in the equation. To do that we just have to divide both sides by (pi * r^2), where we end up with: