Developed by Dr Claus Zinn

Computer Scientist and Educational Researcher

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Lehrer Lämpel

Version 1.1
Lehrer Lämpel: Number Wheels
An educational app that supports primary school kids to train their skills in basic arithmetic.
  • Practising addition and subtraction, as well as multiplication and division
  • Infinite number of (randomised) exercises
  • Immediate Feedback
  • Three levels of difficulty
  • Training and challenge mode (latter, with highscore)
  • Multi-lingual help page (english, german, french)
  • Available for iPad tablets, from iOS7
  • Price: .99 USD, 1.09 Euro
Compatible with the iPad. Requires iOS7 or later. No WiFi, Edge, or 3G network connection required. No ads.


Can you fill-in all the digits so that all calculations are correct?

Lehrer Lämpel: Number Wheels is an educational app that supports primary school children to practise their skills in basic arithmetic.

Easy input of numbers to the blackboard.

Pupils can ask Lehrer Lämpel for help at any time.

Supports infinite number of randomised exercises

Supports English, French and German.

Available on the iPad, for iOS7 or later.


Version 1.0

January 30th 2015
  • NEWInitial Release.

Version 1.1

Released on November 14th, 2015
  • NEWAdded support for iOS9.
  • Improved design


Privacy Policy

Our privacy policy is rather simple. We do not collect any information from you and your child when using our app or browsing our website.

You or your child will never be prompted to provide any sort of information in our app. You are free to use the contact form on the website to give us your feedback, ask questions, elicit new app features, or file a bug report. For this, you can equally contact us at

We will use your contact information only for being able to reply to your requests. It will not be shared with anybody else.

Our app is solely financed by its price tag, there are no in-app purchases, and the app is ads-free.


Contact Us

Please use the following form for questions, feedback, feature requests etc.

Our email:

Postal Address

Dr. Claus Zinn, Diplom-Informatiker (Univ.)
In der Gebhardsoesch 33
78467 Konstanz, Germany