Letters are given their alphabetical values A=1 to Z=26. In each of the four categories, addition, subtraction, multiplication and division, the first and last letters of a 4-letter word work together to give the same result as the second and third letters working together.
"The Inside and Outside of Four Letter Words,"
Word Ways: Vol. 52
, Article 23.
Retrieved from: https://digitalcommons.butler.edu/wordways/vol52/iss4/23