Rule of Proportion simplifies calculations with 3 out of 4 variables, catering to educational needs. Users can input variables, perform calculations, and view detailed solutions. The app features a history function to save inputs and allows sharing of final solutions. Fraction and decimal inputs are supported, along with constants. An ad-free experience is available as well.

The user-friendly interface offers 4 fields for variable input, with error highlighting for incorrect or missing values. Navigation between solution, input view, and history is seamless through swiping or buttons. Users can manage history entries by deletion or manual sorting. Selecting a history entry loads it for automatic calculation, while clearing the entire history is possible with a single action.