Subtractions (Partially Unseen)

After understanding the theory, improvement in mental maths comes from specific focused practice. This tool is designed for you to practise subtracting unseen numbers, for example when calculating change.

How to Use this Tool:

  • Ideally use a desktop browser to make input easier.
  • Select the question type from the drop-down menu.
  • Type the answer as fast as possible when the question appears, and hit [Enter] or the “Go!” button.
  • The tool will check your answer and reveal your time.
  • Hit [Enter] or “Go!” again to move to the next question.
  • After several questions, you can review your speed and accuracy.



Further Notes

  • You can see improvement in just 5 minutes per day of focused practice.
  • Keep a track of your performance—just like an athlete would—to see improvements and plateaus.
  • This tool was developed by Daniel Timms for his students improving their Mental Math ability.