Mental Calculation is a free game for mental calculations.
You can choose additions, subtractions, multiplications, divisions, or a mix of them.
You can choose from level 1 to 9 (all free), depending on your choosing it is getting faster and more difficult, so that it can be used by little ones or adult as well.
This is a perfect exercise for keeping your brain in good health.
The perfect application for adults, but for children too, who want to learn the basics of math having fun.