Hi Kennedy,
I really do not understand your question.
I do not understand the estimation method that you have described and ..
Why would you use any estimation process for this?
Plus is easy and the numbers are not very big.
So I know I am not answering your question Sorry
A typical brick is a rectangular prism with dimensions 4 in. x 2 in. x 8 in.
A typical bathtub is a rectangular prism with dimensions 60 in. x 30 in. x 18 in.
60/4=15
30/2=15
18/8=2.25
The base layer is 15*15=225 bricks
There are 2.25 layers so 225*2.25=506.25 = 507 bricks.
alternatively
4*2*8=64
60*30*18=32400
32400/64 = 506.25 = 507 bricks