Three cubes of metal whose edges are 9, 12 and 21 cm…

Three cubes of metal whose edges are 9, 12 and 21 cm respectively, are melted and one new cube is made. Find the edge of the new cube?

This problem repeats another one in the library (at most with different numbers), so it's left out of browsing.

AQuA-RAT — Algebra Question Answering with Rationales (Ling et al., DeepMind, 2017) · train #49651