A seller uses 800gm in place of 1kg to sell his goods

A seller uses 800gm in place of 1kg to sell his goods. Find his actual % profit or loss, when he sells his article his article on 10% gain on cost price?

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 #47858