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How to find compound interest in c without using pow function

+1 vote
asked Oct 23, 2021 by Diego Lim (130 points)

1 Answer

+1 vote
answered Oct 24, 2021 by Peter Minarik (63,340 points)
edited Oct 25, 2021 by Peter Minarik

Let's see if I get you right.

You would like to invest startAmount at a rate of interestRate and you'd like to know how much money you'll have at the end of n investment periods.

In this case, you'd have the following formula: totalMoney = startAmount * (1 + interestRate)n

, where interestRate is expressed as a floating-point number (e.g. 10% --> 0.10)

Now, you ask how you can do this without raising anything to a certain power.

Well, if you take the basic definition of the ab, it means that you multiply a with itself b times.

In programming terms, instead of using the pow() function, you can write a loop that multiplies a given number of times. E.g.:

float CalculateInterest(float startAmount, float interestRate, size_t n)
{
    float multiplier = 1.0 + interestRate;
    for (size_t i = 0; i < n; i++)
        startAmount *= multiplier;
    
    return startAmount;
}

Is this what you're after?

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