Asp Forum - Re: Ruby math.pow equivalent

Kandem, Vamshi Krishna

3/30/2007 10:00:00 AM

Hi john,

This the answer.

@principal*@rate/(1-(1/(1+@rate))**@payments )

Thanks
VamshiK

-----Original Message-----
From: list-bounce@example.com [mailto:list-bounce@example.com] On Behalf
Of John Butler
Sent: Friday, March 30, 2007 2:52 PM
To: ruby-talk ML
Subject: Re: Ruby math.pow equivalent

Drew Olson wrote:
> John Butler wrote:
>> Hi,
>>
>> I am trying to calculate a monthly payment for a loan in Ruby. Does
>> anyone know what the equivalent for math.pow in Java is for Ruby?
>>
>> @monthlypayment =
@principal*@rate/(1-Math.pow(1/(1+@rate),@payments))
>>
>> Ive searched everywhere and cant seem to find anything.
>>
>> thanks
>>
>> Johnny B
>
> I think this is what you're looking for:
>
> irb(main):001:0> 2 ** 1
> => 2
> irb(main):002:0> 2 ** 2
> => 4
> irb(main):003:0> 2 ** 3
> => 8
> irb(main):004:0> 2 ** 4
> => 16

Yes this is what i am looking for. How do i then use it to calculate
amonthly payment, i have tried quite a few things but cant get the
syntax right: @monthlypayment =
@principal*@rate/(1-**(1/(1+@rate),@payments))

So for the example below:

Suppose you finance your car with a loan of $12000 at a yearly interest
rate of 11% for four years, and make equal payments monthly. How much
will your payments have to be? Here the parameters are principal P =
$12000, interest rate i = 0.11, number of years n = 4, and number of
periods per year q = 12. Then the monthly car payment M is given by

M = Pi/[q(1-[1+(i/q)]-nq)],
= ($12000)(0.11)/[(12)(1-[1+(0.11/12)]-(4)(12))],
= $110/(1-1.009166666...-48),
= $310.15.

Anyone done this before?

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comp.lang.ruby

Re: Ruby math.pow equivalent

Kandem, Vamshi Krishna

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