According to this NHK medical frontiers show [0][1], Japanese researchers demonstrate that doing daily basic math exercises and reading aloud is good for the brain. So I built a basic math exercise generator app [2].

[0] https://www3.nhk.or.jp/nhkworld/en/tv/medicalfrontiers/20170... [1] https://www.youtube.com/watch?v=qr-5urj2WKY [2] https://play.google.com/store/apps/details?id=com.brainmath