Answer 1:
I'm not entirely certain what the fluffiness
of a cake is, but if I'm right in that it's air
inside of the cake, then you can measure its
density.
Step one: weigh the cake. First take a plate,
and weigh it on a scale. Then, put the cake on
the plate, and now weigh the cake and the plate
together. Subtract the weight of the plate alone
from of the cake plus plate together. This will
get you the weight of the cake. Equation:
weight of cake = weight of cake and plate 
weight of empty plate
Step two: calculate the volume of the cake.
If the cake is square, then the volume is the
length of the cake, times the width of the cake,
times the height of the cake. If the cake is
round, then the volume is one half of the
diameter of the cake, squared, multiplied by pi,
and then multiplied by the height of the cake.
Pi is roughly 3.14 (it's not exact, but it's
close enough for your purposes. So,
equations:
square cake:
volume = length x width x height
circular cake:
volume = (diameter / 2) x (diameter / 2) x
height x pi
pi = 3.14
Step three and finally: calculate the density of
the cake. Divide the weight by the volume.
Density = weight / volume.
Now, this number isn't going to help you
unless you have another cake to compare it to.
You will need to repeat this procedure for each
cake you need the density for, but once you have
the densities, you can compare them.
A cake with a lower density, that is less
weight of cake per unit volume, will be a
fluffier cake.
