The main purposes of this paper are to probe for the entropy differences between arithmetically manipulated triangular fuzzy numbers (TFNs) using Shannon’s function and to study the relationships between any two TFNs. Simultaneously, we expand on Wang and Chiu’s article [9]. The entropy differences between two TFNs subjected to different arithmetic operations are classified as fifteen theorems, and fifteen examples are used to prove the accuracy of these theorems. This paper finds that with the application of Shannon’s function on triangular fuzzy numbers, the grades of fuzziness are changed after arithmetic operations.