The average of 20 numbers is zero

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

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 #4534