HP HP-11C - Page 55

Section 3: Numeric Functions 53
Combination. Pressing calculates the number of
possible sets of y different items taken in quantities of x items at a
time regardless of order (where no item occurs more than once in a
set). calculates combinations by the following formula:
y!
c,,= ————
»x x!(y —x)!
To execute a permutation or combination:
1. Keyinthe number of items (y).
Press [ENTER].
Key in the quantity of items required (x) per arrangement or
set.
4. Press[f][Py.x]or[g][Cr.x].
T t
Z+ t
Y - z
X p or
cove>
or [g][Crx] LAST X
The result, p or ¢, will appear in the displayed X-register, the stack
will drop, and the quantity per arrangement or set (x) is placed in
the LAST X register.
All permutation and combination inputs must be non-
negative integers.
Note: The execution times for and calculations
can be several seconds or longer, depending on the
magnitude of your y and x inputs. The maximum value you
can input for a or calculation is 10'0 — 1. The
running message will flash in the display during execution of
(Pr,x]Jand [Cy,x]calculations.