The Sum of first N consecutive odd integers is N^2

The Sum of first N consecutive odd integers is N^2. What is the sum of all odd integers between 9 and 39 inclusive.

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 #3859