Integer arithmetic and order of operations

Computers perform calculations constantly. This is the foundation of all data processing. The four basic operations are addition (+), subtraction (−), multiplication (·), and division (/).

Order of operations: Multiplication and division are performed before addition and subtraction. Example: 2 + 3 · 4 = 2 + 12 = 14, not 20. If you want the addition to happen first, use parentheses: (2 + 3) · 4 = 20.

The computer always follows this logic. To get the correct result in code or spreadsheets, you must follow the same rules.

Calculate the result before verifying:

10 − 2 · 3   →  4      (multiplication first)
(10 − 2) · 3 →  24     (parentheses first)
12 / 4 + 1   →  4
12 / (4 + 1) →  2.4

Construct your own expression where parentheses change the result. Construct an expression where they do not.