HP 20B - Manual (Page 17)

Mathematical Calculations
17
Chain Mode
Calculations in Chain mode are interpreted in the order in which they are entered. For example, entering the following
numbers and operations as written from left to right
1+2*3=
returns 9 . See Figure 2.
Figure 2 Calculation in Chain Mode
Note: if you press an operator key,
+-*/
, after
=
, the calculation is continued using the currently
displayed value.
In Chain mode, if you wish to override the left to right order of entry, use parentheses
()
to prioritize operations.
For example, to calculate
 
3 2 1
  , you may enter the problem as written from left to right, with parentheses to prioritize the
multiplication operation. See Table 2-1 below.
Table 2-1 Simple Arithmetic Calculations in Chain Mode
Keys Display Description
1+
(2*3) Sets operational priority, inputs numbers, and
multiplies 2 and 3.
= Adds 1 to 6 and returns 7.00 on the bottom line as
the final result.
Algebraic Mode
To set the calculator in Algebraic mode, refer to the section titled, The Mode Menu: Setting Preferences in Chapter 1 .
In Algebraic mode, multiplication and division have a higher priority than addition and subtraction. For example, in Algebraic
mode, pressing
1+2*3=
returns a result of 7.00 . In Chain mode, the same key presses return a result
of 9.00.
In Algebraic mode, operations between two numbers have the following priority:
 Highest priority: the power function (y x )
 Second priority: combinations and permutations
 Third priority: multiplication and division
 Lowest priority: addition and subtraction