Magnetic Letter and Number Fishing. They add/multiply what they catch.
SAMEN MET GROVE MOTORIEK
This could be done with sight words, numbers, letters of the alphabet, etc!
Dice game 2 to 5 players First player that gets to the end of their lane wins 5 tickets. You must roll the same number of spaces you have left to win at the end of your lane. All players that don't win get 1 ticket.
Doing math in your head (like the Germans) is easier if you think in blocks of 10. Here's a fantastic graphic for school kids that can help you build up the skill of doing math in your head. (I couldn't do it until I moved to Germany and learned the metric system--now it's quick and easy for me to do math in my head!)