The crossword solutions for the term USE AN ABACUS, MAYBE are 'ADD', which is a three letter word. The term 'ADD' is an abbreviation for the mathematical operation of addition. Addition is a basic arithmetic operation that involves combining two or more numbers to produce a sum. An abacus is a tool used for counting and calculating, and it can be used to perform addition. Therefore, the term USE AN ABACUS, MAYBE suggests that one should use an abacus to perform addition, rather than relying on mental calculations.