[Overview] This is a calculator that allows you to check the formula in the middle of a fraction. It is designed for the purpose of making it easier for supervisors such as learning leaders to find the location of calculation errors. [Major features] 1) Press the “=” button to switch to the fractional mode and the intermediate formula for fractional calculation will be displayed. 2) Not only arithmetic operations of fractions but also mixed numbers, decimals and negative numbers are supported. 3) Click the “=” button or the calculation result display area to hide the fraction screen and use it as a calculator mode like a normal calculator (continuous calculations are possible). Students should not use it unless they can't find the calculation error (the calculation power will be reduced).