You can do many things with mathematical knowledge in your life. For example, you can calculate some addition, subtraction, multiplication and division, buy food or go to the supermarket. And you can estimate the data according to the actual situation, for example, you can know the distance and speed.

Calculate the travel time. Such as the length and width of the house, calculate the approximate area of the house. For example, when doing experiments, know the voltage and resistance to calculate the current and power. The list goes on and on.