A river boat leaves Silver Town and travels upstream to Gold Town…

A river boat leaves Silver Town and travels upstream to Gold Town at an average speed of 4 kilometers per hour. It returns by the same route at an average speed of 7 kilometers per hour. What is the average speed for the round-trip in kilometers per hour?

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 #21366