When the price of an article was reduced by 40% its sale…

When the price of an article was reduced by 40% its sale increased by 80%. What was the net effect on the sale?

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 #6127