HP 20B User Manual

Mathematical Calculations
27
 nCr
 nPr
Y
x
is the power function, nCr stands for the number of combinations of n items taken r at a time, and nPr stands for the
number of permutations of n items taken r at a time.
Combination=
  !!
!
rnr
n

Permutation=
  !
!
rn
n

Perform calculations with these functions in the same way you would perform calculations with +-/ and *,
but press : to access the secondary function key. For example, to calculate 15
3
:
1. Press 15.
2. Press :h.
3. Press 3=. The results are shown Figure 9.
Figure 9
In RPN mode, key in the numbers first, followed by I, then press the function key. For example, for the power function
example above, in RPN press: 15I3:h.
Storing and Recalling Numbers
The calculator has ten memories available for use during calculations. These memories are numbered from 1-9 and 0. To
store a number in a memory, press :$, followed by the key representing the memory number. To recall a number
stored in a memory, press L followed by the key representing the memory number. You can use the store and recall
functions for these memories any time a number is displayed, or when you wish to enter a number.
For example, to store 15 in memory 1, press 15:$1.
To recall the number in memory 1, press L1.
You can also perform operations to numbers stored in memories. For example, press 5:$2 to store 5 in
memory 2. To add 12 to the value of memory 2, press 12:$+2. Later on, during a calculation, you can

HP 20B Specifications

General

Type	Financial
Cover	-
Form factor	Pocket
Control type	Buttons
Product color	Black
Digits	12 digits
Display type	LCD
Display tilting	No
Display number of lines	2 lines
Battery type	CR2032
Power source	Battery
Auto power off	Yes
Number of batteries supported	2
Memory registers	110

Weight and Dimensions

Depth	149.2 mm
Width	77 mm
Height	16 mm
Weight	37.5 g