HP 10B - Manual (Page 131)

Case 5. The calculator displays; no Solution. There is no answer.
This situation might be the result of an error, such as a mistake in
keying in the ca.sh flows. A common mistake that results in this mes*
sage is putting the wrong sign on a cash flow. A valid cash-flow .series
for an IRR/YR calculation must have at least one positive and one
negative cash flow.
Halting and Restarting iRR/YR
The search for IRR/YR may take a relatively long time. You can hall the
calculation at any lime by pressing the O key. The message IntErruPlEd
is displayed. Pressing 0 now displays the current estimate for IRR/YR.
You can resume the calculation by;
■ Pressing (STOI IQEBZYQ while the current estimate is displayed in
the calculator line. This continues the calculation from where it left
off.
Storing a guess for ¡RR/YR, discussed below.
Entering a Guess for IRR/YR
To enter a guess, key in an estimate of IRR/YR and then press fstol
BlIRR/YRi. You can enter a guess for IRR/YR at these limes;
■ Before beginning the calculation. A fairly accurate guess can reduce
the time required to calculate an answer and reduce the chance of the
calculator solving for an undesirable negative solution.
■ After you’ve interrupted the calculation.
■ After the calculator has halted the calculation due to any of the
aforementioned eases. However, for cases 3 and S, no other solutions
will be found.
When calculating IRR/YR using a guess, the calculation halts when it
finds an answer. However, there may be additional positive or negative
answers, or no true solution at all. You can continue searching for another
.solution by hailing the calculation and entering a difTcrent guess.
One way to obtain a good guess for IRR/YR is to calculate the NPV for
various interest rates. Since IRR/YR is the interest rate at which NPV
equals zero, the best estimate of IRR/YR is the interest rate that yields
the value for NPy clo.sest to zero.
128 B: More About CafculaUont