I did this quiz a few times in a row and finally got more than average. It's been a while since I had to do this quickly. Got a good technique now. Maybe I'll get 100% soon.
The caption is a bit weird in my opinion. On top of being gramatically wrong. How about "Schnelles Kopfrechnen - Multiplikation" (which is what people would actually call this in school)? The school subject "Mathematik" in Germany technically includes "rechnen", but "Kopfrechnen" or just "rechnen" is much better for this quiz. "Mathematik" can't really be fast (and if it could be, you would say "schnelle Mathematik"). And anyway I mostly think about equations, matrices, trigonometry, proofs and all kinds of advanced stuff when I read "Mathematik". Please change that?
"Schlagen Sie die Uhr BEI der Beantwortung dieser zufällig generierten Multiplikationsaufgaben."
"Die Zahlen ändern sich bei jeden Spielen" (meaning that the numbers change in each new game) makes more sense than
"Dieses Quiz wechselt mit jedem spielen!"
Mit einem Taschenrechner ist Betrug :)