Kopfrechnen-SchnickSchnack play online

If the basic arithmetic (GRA) ADD, SUB, MUL, DIV will not be repeated again and again in the early stages, the mathematical foundation will always be uncertain.
Therefore you win by the GRA-APP no frills safety in mental arithmetic.

By the targeted setting the number spaces (lower limit UG / OG upper limit), the exercises can be adjusted individually.

Since I do not want to finance with advertising my programming effort, there is still a price favorable GRA + app that logs the exercises.
The protocol used for error analysis:
- Zahlendreher
- Problems with regrouping
- time improvement
- loss of concentration when occur in the final part heaped error

Here GRA +: https://play.google.com/store/apps/details?id=appinventor.ai_widabsemper.GRA_plus