For a year now, incidence values have been determining the assessment of the pandemic - and thus the measures to contain the virus and life in Germany.
But the number also depends on how much is tested in a district.
If the test strategy of the federal and state governments works, more and more new cases will be discovered because a positive rapid test is followed by a reliable PCR test.
The incidence rises almost automatically.
The problem is known.
A student teacher for mathematics and physics from Bad Reichenhall has developed a possible solution.
And that is, says Patrick Schönherr, 23 years old, easy to understand even for non-mathematicians - material from the middle school.