I often have to compute the net present value of monthly payments of say 100,00 kr. on 240 consecutive months with an interest rate of 0,05% pr year.
In SMATH the summation goes from k=1 to k=240 of the calculation -100/(1+0,05/12)^k, and the result is
-21063,356, but the same calculation in MathCad and Excel computes to -15152,53.
It seems that the summation is correct in the interval k=1 to k=130, but from 131 upwards the calculation is
increasingly wrong compared to MathCad's solution.
The counter variable seems correct, so I can't figure out what goes wrong. Is there a problem or am I mistreating the program in some way (like I did with the "solve" function)?
I tried the same summation with the for-loop, and got the same result (-21063,356), and also found that the for-loop summation is correct up to 130 as the upper limit of the loop-counter.

Edited by user 10 April 2009 17:15:55(UTC)  | Reason: Not specified