Drew O. wrote:

John B. 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?