More About HP-18C
Calculations
IRRO/o
Calculations
B
The
HP-18C
calculates IRR% for a set of
cash
flows
using
mathemati-
cal
formulas
that
"search" for
the
answe
r.
The
process finds a
solution
by
estimating
an
answer
and
then
using
that
estimate
to
do
another
calculation-in
mathematical
terms,
an
iterative process.
In
most
cases,
the
HP
-18C finds
the
correct answer, since
there
is
usually only
one
solution
to
the
calculation. However, calculating
IRR% for certain sets
of
cash
flows is
more
comp
l
ex.
There
may
be
more
than
one
mathematical
solution
to
the
problem
,
or
there
may
be
no
solution
. In
these
cases,
the
HP-18C
displays a message to
help
you
interpret
what
has
happened.
Possible Outcomes of Calculating IRR%
These are
the
possible
outcomes
of
an
IRR% calculation for
which
you
have
not
stored
a guess. Storing a guess is covered
on
page
170 .
•
Case
1:
The
HP-18C
displays
a positive
answer
. This is
the
only
positive answer. However,
one
or
more
negative
answers
may
exist.
•
Case
2:
The
HP-18C
displays a
negative
answer
and
the
message:
IRR%>0
EXISTS;
TO
SEEK :
INPUT GUESS
[STO]{IRR%}
The
HP
-18C
has
detected
that
there
is a single positive answer.
To
search
for
that
positive answer, you
must
input
a guess. (Refer to
Storing
a
Guess
for
IRR%
on
page
170).
There
may
also
be
one
or
more
additional
negative
answers
.
B:
More
About
HP-18C
Calculations
169