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Some speed tests comparing old and new HP 15 LE

Lets now do some speed calculations between the 2 models - old and new:


Let`s try to calculate a 10-year IRR with the following program, which uses the solve function on the following Net Present Value program:



2 - from % to decimal




1/x - calculate 1/(1+i)



ENTER - to load the stack with 1/(1+i)

RCL .1 - number of periods (so that is is kept for further trials with other interest rates)



LBL .2 - loop for periods

RCL + (I)

X - calculates f(n) = (f(n-1)+ I(n))/(1+i)


GTO .2 - Return if not 0

RCL + 0 - Add start cashflow


Let`s now try with the following cash flow

Initial -126.000

year 1 3.750

year 2 2.750

year 3 4.000

year 4 5.000

year 5 4.000

year 6 5.000

year 7 4.000

year 8 5.000

year 9 4.000

year 10 250.000

We put a starting value of 5%, to get it started.

With the old one: we launch, and wait, and wait, ..., and wait,...3' 34 secs. This program is a nice help for my financial job, and useful for short examples of up to 4 years - but completely impractical for business. Imagine a meeting room waiting for your results, if the cashflow to analyze is 10 years.

With the new one, around 1,5 seconds. We're in business !!!

By the way, both gave the same result, up to ten digits accuracy: 9,389956649%. This is yet another proof that both calculators share firmware.(let's be accurate - it is not a proof, but a hint)

Let's try now with the standard Time Value of Money program that appears in the advanced functions manual. And let's try with the longest function - the calculation of i for a formula

New model: around 1 sec.

Old model: 53 seconds.

A banker could not wait that long for an answer! However, the new one is acceptable for business.

I have tried to put a couple of comparisons of programs and situations that may happen in reality - not just a closed loop that no one will ever use. In this view, the new calculator allows for a number of applications that the former one could not do in a practical way.

Other example: inversion of a simple 4x4 matrix

Old 15c: 10 seconds

new 15c: clearly less than 1 second

(in this case both units were practical for use in an examination - more so because no modern teacher would suspect that a so humble calculator could do matrix inversion!!)

Next day we will talk about the look and feel.

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