Pipe A can fill a tank in 6 hours, pipe B in…

Pipe A can fill a tank in 6 hours, pipe B in 18 hours and pipe C in 36 hours. If all the pipes are open, in how many hours will the tank be filled ?

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 #56352