244 Appendix C: More About
L
File name: hp 12c pt_user's guide_English_HDPMF123E27 Page: 244 of 275
Printed Date: 2005/8/1
Dimension: 14.8 cm x 21 cm
Searching for IRR.
You can continue searching for IRR solutions, even after an
Error 3
indication, as follows:
1. Make a guess for the interest rate and key it in.
2. Press
:gt
.
Your guess will aid the calculator in its search, and if it finds an
IRR
answer near
your guess, that answer will be displayed. Since the calculator cannot tell you the
number of solutions that exist when there is more than one mathematically correct
answer, you can continue to make guesses, pressing
:gt
after each one,
to search for
IRR
solutions.
You can hasten this process by using the
l
function to help you make a good
guess. Remember that a correct
IRR
solution will make the calculated
NPV
very
small. So continue to guess interest rates and solve for
NPV
until the answer you
obtain is reasonably close to zero. Then press
:gt
to calculate the
IRR
answer near your guess.
How would this work in case 2 above
?
The calculator displays a negative answer
and you wish to check for a unique positive
IRR
. Key in successively larger guesses
for
i
(starting from 0) and solve for
NPV
until you reach a sign change in your
NPV
outcomes. Then press
:gt
to find an
IRR
solution near the last interest rate
obtained using the
l
key.
If you stop the
IRR
iterative process, you can test the interest obtained using
l
,
and then restart the process by pressing
:gt
.