PLCs use four different basic math instructions. ADD, SUB, and DIV are three of the instructions. What is the fourth basic PLC math instruction?

The fourth basic math instruction commonly utilized in Programmable Logic Controllers (PLCs) is multiplication, represented as MUL. This instruction is crucial for various industrial applications where calculating products or scaling values is required.

In the context of basic PLC instructions, the four essential arithmetic operations—addition, subtraction, division, and multiplication—enable the PLC to perform a wide range of calculations necessary for process control and automation.

While other arithmetic operations like MOD (modulus), EXP (exponentiation), and SQR (square) serve specific purposes and may be utilized in specialized applications, they are not classified as fundamental arithmetic operations in the standard set of PLC instructions. Therefore, multiplication stands out as the correct fourth instruction alongside the others mentioned. This understanding is vital for effectively programming and deploying PLCs in industrial settings where reliable mathematical calculations are imperative for automation tasks.