Texas Instruments TI-73 Explorer Manual Book page 58

52
Chapter 2: Math Operations
³
nCr
:
b
2
ABCD
! ! 1 " " 5 5
!
³
:
b
4!
ABCD
1 " "
4
combinations of
4 items taken
2 at a time
1 " "
4
ABCD
BACD
CABD
DABC
4
AB AC
BA BC
CA CB
DA DB
5
24 possible arrangements
ABDC ACBD ACDB
BADC BCAD BCDA
CADB CBAD CBDA
DACB DBAC DBCA
AB and BA count
as only one
AD
combination.
BD
CD
DC
4! = 4Q3Q2Q1
ADBC ADCB
BDCA BDAC
CDAB CDBA
DCAB DCBA