Arithmetic is the foundation of mathematics. It studies the four operations between real numbers (natural numbers, integers, decimals, fractions ...), even including the algorithm of square root.

Mathematics can be regarded as an extension of arithmetic. When we use letters to represent numbers and introduce concepts such as equations and functions, the arithmetic originally calculated for actual numbers becomes elementary algebraic operation. When we introduce the concepts of line segments and straight lines and extend arithmetic to the calculation of graphics, arithmetic becomes the reasoning proof of geometry; And if we use algebraic expressions and equations to represent curves, arithmetic serves analytic geometry; When we introduce the dimension of angles, arithmetic helps triangles; When we deduce the unknown into the category of equation, it becomes the field of higher mathematics. ...

Therefore, if you learn arithmetic well, you can master the most basic mathematical foundation. Arithmetic is the premise of mathematics, and mathematics is the extension of arithmetic. If you don't learn arithmetic well and have a weak foundation, then math study must be like a gobbledygook.