Masses are related by their volumes.
If two solids are similar their volumes are related to their corresponding lengths by their cubes in this way:
If a length of solid A has length "La" and the corresponding length of solid B has length "Lb"
and if the volume of solid A has volume "Va" and the volume of solid B has volume "Vb",
then: Va / Vb = (La)3 / (Lb)3.
Also, for areas (by their squares): Aa / Ab = (La)2 / (Lb)2
Let's use this area relationship to find the lengths and then use these lengths to find the volumes.
Aa / Ab = (La)2 / (Lb)2 ---> 40.32 / 28 = (La)2 / (Lb)2 ---> sqrt(40.32) / sqrt(28) = La / Lb
Now, let's use the volume formula ---> Va / Vb = (La)3 / (Lb)3 ---> Va / Vb = [ sqrt(40.32) ]3 / [ sqrt(28) ]3
Va = [ sqrt(40.32) ]3 = 256.024 Vb = [ sqrt(28) ]3 = 148.162
We can now use these values for the volumes to find the mass of A:
mass(A) / mass(B) = Va / Vb ---> mass(A) / 6912 = 256.024 / 148.162
---> mass(A) = 11944 grams
Make sure you're learning from this and not just looking for the answers!!
Check the answer given at : https://web2.0calc.com/questions/math-problem_67#r1 where you first asked it. Don't repeat a question without checking the original!
NB Geno made a slight mistake by inverting the ratio on the RHS.
But if A is smaller then B and they are made from the same material, how is the answer 11943.94?