HP 15c User Manual
Page 26
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Section 1: Using
_ Effectively
26
compounding period—months or years, for example. Vertical arrows represent exchanges of
money, following the convention that an upward arrow (positive) represents money received
and a downward arrow (negative) represents money paid out. (The examples that follow are
illustrated using cash flow diagrams.)
Pressing ´CLEARQ provides a convenient way to set up the calculator for a new
problem. However, it isn't necessary to press ´CLEARQ between problems. You
need to reenter the values of only those variables that change from problem to problem. If a
variable isn't applicable for a new problem, simply enter zero as its value. For example, if
PMT is used in one problem but not used in the next, simply enter zero for the value of PMT
in the second problem.
The basic equation used for the financial calculations is
0
)
100
/
1
(
]
)
100
/
1
(
1
[
100
/
n
n
i
FV
i
i
A
PMT
PV
where i ≠ 0 and
A =
1
for end-of-period payments
1 + i/100
for beginning-of-period payments.
The program has the following characteristics:
_ is used to find i. Because this is an iterative function, solving for i takes
longer than finding other variables. It is possible to define problems which cannot be
solved by this technique. If _ can't find a root, Error 4 is displayed.
When finding any of the variables listed on the left below, certain conditions result in
an Error 4
display:
n
PMT = −PV i/(100 A)
(PMT A – FV i/100)/(PMT A + PV i/100) ≤ 0
i ≤ −100
i
_ can’t find a root
PV
i ≤ −100
PMT
n = 0
i = 0
i ≤ −100
FV
i ≤ −100