Since the 2 solids are similar and made from the same material, then their masses should be proportional to their surface areas:
[28 cm^2 / 40.32 cm^2] x 6,912 =4,800 grams - the mass of A
+9479 We are given that the solids are made from the same material, which means they have the same density.
Since mass = density * volume
massA / massB = (densityA * volumeA) / (densityB * volumeB)
densityA = densityB so we can cancel them out
massA / massB = volumeA / volumeB
So here we have shown that the ratio of the masses is equal to the ratio of their volumes.
Now we need to be careful and remember that the ratio of their volumes is not equal to the ratio of their surface areas.
The ratio of their volumes is equal to the ratio of their surface areas raised to the power of 3/2
(See https://www.onlinemathlearning.com/similarity-area-volume.html )
volumeA / volumeB = ( SAA / SAB )3/2
Now we can replace volumeA / volumeB with massA / massB
massA / massB = ( SAA / SAB )3/2
Now let's plug in what we know for values of massB , SAA , and SAB
massA / 6912 = ( 28 / 40.32 )3/2
Multiply both sides by 6912 and simplify.
massA = 6912 * ( 28 / 40.32 )3/2
massA = 4000 and that is in grams
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+118667 Thanks Hectictar
With any two similar objects A and B
If a pair of corresponding sides are in the ratio \(l_A:l_B\)
then
Pairs of corresponding Surface areas will be in the ratio \((l_A)^2:(l_B)^2\)
And for 3 dimensional objects the volumes will be in the ratio \((l_A)^3:(l_B)^3\)
+1641 Let a side of a hexagon be equal to the height (or length) of a solid.
Solid A A = 28 cm2
I'm gonna use this formula to calculate a2 ( and b2)
2(3√3*a2/2) + 6a2 = 28 a2 = 2.5008485 a = 1.581407127
V(A) = 3√3/2 * a = 10.27502675 cm3
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Solid B A = 40.32 cm2
2(3√3*b2/2) + 6b2 = 40.32 b2 = 3.601221843 b = 1.897688553
V(B) = 3√3/2 * b = 17.75524625 cm3
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
V(B) : 6912 = V(A) : x
x = 4000 grams 
