The average of 20 numbers is zero

The average of 20 numbers is zero. Of them, How many of them may be greater than zero, at the most?

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 #9862