We have no dimensions to work with. I'll pick some and try and comply with the conditions of the problem.
Suppose you have an object that is 14 by 22 by 27 cm. These three numbers have no common factor so they cannot be reduced any further, which is helpful for this problem.
Find the Volume
Volume
l = 27 cm
w = 14 cm
h = 22 cm
V = 27 *14 * 22
V = 8316 cm^3
Find the surface area
SA = 2*l*w + 2*l*h + 2*w*h
SA = 2*27*14 + 2*27*22 + 2*14*22
SA = 756 + 1188 + 616
SA = 2558
Just looking at these numbers The surface area is about 1/3 of the volume. I don't think this is always true.
Another way to do this is to consider a cube which might give you a more useful result.
s = L = W = H all three dimensions are equal in a cube.
The volume of a cube is s*s*s = s^3
The surface area of a cube is 2*s*s + 2*s*s + 2s*s = 6s^2


That means whatever the side length, the Surface Area to volume = 6/the side length which is kind of an interesting result.
Complete 2/3 x the number of plates
Let's start with what we know:
Smaller canvas:
Length (

) = 3ft
Width (

) = 5ft
Larger canvas:
Length (

) = ?
Width (

) = 10ft
Since these are similar rectangles, we can cross-multiply to calculate the missing length. Here's that formula:

So let's plug it all in from above:

Now we cross multiply by multiplying the top-left by the bottom-right and vice versa:


Now divide each side by 5 to isolate


The 5s on the right cancel out, leaving us with:

So the length of the larger canvas is
6 ft