How would you go about finding the surface area of a galvanized washer?

because theres a whole in the middle and it has curved 3D edges, what would be the best way to determine the total surface area?How would you go about finding the surface area of a galvanized washer?
pi*r^2(big circles area) - pi*r^2(little circles area) to find the surface area of one side so just double that, to find the surface area of the 3D edge as you call it its a simple length * width multipliction so you will need to know the width of the washer and its circumference (distance around its edge).How would you go about finding the surface area of a galvanized washer?
First pretend the washer is a solid cylinder of radius r₁ and height h.


lateral area =2πr₁h


top area = base area =πr₁²


total surface area A₁ = 2πr₁h + 2πr₁²





Now pretend the hole is a cylinder of radius r₂ and height h.


lateral area =2πr₂h


top area = base area =πr₂²





You cannot simply subtract the surface area of the hole from the surface area of the solid. The lateral area of the hole is part of the washer.





surface area of washer = A₁ + lateral area of hole - top and base of hole


= 2πr₁h + 2πr₁² + 2πr₂h - 2πr₂²
Okay I have no idea what a galvanized washer is but if you're finding the surface area of a box, this is how i do it:





Length * Width ----%26gt; will give you area of one face


Length * Height-----%26gt; will give you area of another face





Add the two products together and multiply by 2 will give you surface area of 4 sides





Then multiply Width by Height


Multiply by 2





Add it to the previous sum





Now that's the total surface area. I'm not sure what you meant by whole, but if you just made a spelling mistake and meant hole, it doesn't affect the surface area. If there is a 3D hole in the middle it isnt part of the outside





Hope i helped, sorry if i confused you


Didn't really understand anything
use the equation (2 times 3.14 times radius) of the full circle and the small circle subtract small s.a form big s.a to get total s.a, radius is half the length of the big and small circle then times total surface area by the width