Why, if I enter “1 + 2 x 3 =” do I get 7 and not 9?
The order in which arithmetic operations is carried out is called precedence. Calc defaults to algebraic precedence which is the way most scientific calculators work. This means that multiplication takes precedence over addition, which is equivalent to 1 + (2×3) = 7 because the multiplication is evaluated first, even though it was the second arithmetic operation entered . Some calculators (particularly very simple ones) do not use algebraic precedence and only the order of entry is significant, so (1 + 2) x 3 = 9. Calc can be configured to use either type of precedence by clicking the Mode button and selecting the Mode tab. There is a section on this tab page called “Precedence” which gives you three options: As Entered, Algebraic (the default) and a third option “RPN” (Reverse Polish Notation; a very elegant solution which allows you to enter complex expressions without using parentheses, and made popular by Hewlett Packard’s calculators). If you switch to “As Entered” mode, the calcu
