Mathematics is a universal language for understanding our world. I will show in this talk several examples how I as a mathematician have been using mathematics to understand observations I encountered throughout my life. I will explain for example how one can hear the speed of a motorcycle, how a computer plays sudoku, how to cut a donut into as may pieces as possible with three cuts, how a dog runs after a jogger, how speed affects gas use when driving a car, how to win a famous TV show, circular billiard, and how not to cook a chicken in a microwave oven.