The mean of 50 observations is 200

The mean of 50 observations is 200. But later he found that there is decrements of 9 from each observations. what is the the updated mean is ?

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 #52383