chromium has four naturally occurring isotopes; cr-50, cr-52, cr-53, and cr-54. if the average atomic mass of chromium is 51.996 amu, which isotope of chromium is found in the greatest abundance?

It depends on the subject for me. some exams are easier than others so i usually go through it and answer questions i know based on my general knowledge, then double check after. going through the lesson can a lot  because the exams can be  very lesson-specific, but sometimes they are ridiculously long so a lot of people don't take the time. i did find that, when i went through the lessons, i was making 100's on my exams vs strictly using + the internet and  i make 90's.