Maths-Rounding

If you don't know much about it:

https://www.khanacademy.org/math/pre-algebra/pre-algebra-arith-prop/pre-algebra-rounding-whole-numbers/e/rounding_whole_numbers

https://www.mathsisfun.com/rounding-numbers.html


If you want to give it a go:

https://www.free-training-tutorial.com/rounding-games.html

https://www.topmarks.co.uk/Flash.aspx?f=DartboardRoundingv2

https://www.mathnook.com/math/skill/roundinggames.php