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Pile A is a cube of unit cubes plus 1 single unit cube. Pile B has exactly the same number of unit cubes: a cube plus one more solid cube. What is the edge of that orange cube?

Class 8Cubes and Cube RootsCubes and Roots
  • A9
  • B3
  • C11
  • D729

Step-by-Step Solution

Pile A has cubes. Pile B: , so the edge is 9. (1729 is the Hardy–Ramanujan number.)
Answer: A) 9

Key idea: Squares vs cubes — what's different

Both are repeated multiplication, but with key differences:

- A square is non-negative: .
- A cube **keeps the sign**: . (Three negatives stay odd → still negative.)
- Squares grow more slowly than cubes: vs For square roots, only positive results (by convention). For cube roots, the sign matches the input: ∛.

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