In this video, I solve and explain a variety of mental math problems where we operate near so many thousands. For example, if you have 2,965, how much is missing from the next multiple of thousand (which is 3,000)? We also look at subtractions where you subtract from a multiple of thousand (e.g. 8000 - 36) and study the error of estimation a little bit.
Math Mammoth Grade 4 curriculum
https://www.mathmammoth.com/complete/grade_4