Math Apps for IPads, computers, etc.
Xtra Math (fact practice)
Times tables (fact practice)
Math Edge (flash cards) - you can choose what operation you want to practice
MathPop - choose grade 4
Speed Drill - practice facts at a fast pace
Turbo Math
4th Grade Math - Common Core math practice
Prodigy play.prodigygame.com
Cool Math Games https://www.coolmathgames.com/
NeoK12 https://www.neok12.com/