Sumdog is a way for kids to practice math skills while playing fun, math-related games against friends, classmates, or students from around the world. Games are individualized for each kid’s ability level, so users can play against opponents who have the same skills. This is a free app. A subscription to Sumdog Premium provides more games.
Sumdog website – https://www.sumdog.com
iTunes link – https://itunes.apple.com/ca/app/sumdog/id1145809959?mt=8