In the IELTS exam, you will be docked points for wrong spelling. While most students spend a lot of time learning vocabulary, or understanding how the exam works, they often forget to learn how to spell.
Sometimes the reason we say words wrong is because we don't know the right rules. There are actually two ways to pronounce "-ate" words: /-eit/ (as in "eight" or "ate") and /-it/. To know the correct pronunciation, you have to know the function.