Question

100x100x100,bases 2 and 5

Answer 1

100x100x100 = 1000000 regardless of base.

Now, if you mean (100₁₀x100₁₀x100₁₀)₅ that's different:

(100₁₀)₅ = 400₅

working in base 5, 400x400x400 = 4^3*1000000 = 224000000