HP·38E/38C - Slide Rule Museum
HP·38E/38C - Slide Rule Museum
HP·38E/38C - Slide Rule Museum
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More About IRR 137<br />
Searching for IRR. You can continue searching for IRR solutions,<br />
even after an Error 3 indication, as follows:<br />
1. Make a guess for the interest rate and key it in.<br />
2. Press I RCL I []] (]ill .<br />
Your guess will aid the calculator in its search, and if it finds an IRR<br />
answer near your guess, that answer will be displayed. Since the calculator<br />
cannot tell you the number of solutions that exist when there is more<br />
than one mathematically correct answer, you can continue to make<br />
guesses, pressing I RCL I[]] (]ill after each one, to search for IRR<br />
solutions.<br />
You can hasten this process by using the Liliil function to help you make<br />
a good guess. Remember that a correct IRR solution will make the calculated<br />
NPV very small. So continue to guess interest rates and solve for<br />
NPV until the answer you obtain is reasonably close to zero. Then press<br />
I RCL I[]] (]ill to calculate the IRR answer near your guess.<br />
How would this work in case 3 above? The calculator displays a negative<br />
answer and you wish to check for a unique positive IRR. Key in successively<br />
larger guesses for [IJ (starting from 0) and solve for NPV<br />
until you reach a sign change in your NPV outcomes. Then press<br />
I RCL I[]] (]ill to find an IRR solution near the last interest rate obtained<br />
using the Liliil key.<br />
If you stop the IRR iterative process, you can test the interest obtained<br />
using I NPV I, and then restart the iteration by pressing I RCL I[]] (]ill.
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