Pipe A fills a tank in 12 minutes

Pipe A fills a tank in 12 minutes. Pipe B can fill the same tank 3 times as fast as pipe A. If both the pipes are kept open when the tank is empty, how many minutes will it take to fill the tank?

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 #73587