"DanielLee" <dlh3648@[EMAIL PROTECTED]
> wrote in message
news:1122232333.530944.188010@[EMAIL PROTECTED]
>
> Hi,
>
> Lets say (for example) that I convert $1,000 dollars to Mexican pesos
> at 11% and end up with $11,000 pesos.
First, exchanging $1,000 for 11,000 pesos is not an 11% exchange rate.
It's
an 1100% exchange rate. (Review the definition of "percent.")
>
> Now lets say I want to convert $11,000 pesos to dollars at the same
> rate. The way I am doing it now would be to multiply the $11,000 pesos
> x .090 which gives me $990 dollars, I am missing $10 dollars.
>
> How do I figure out what the peso to dollar exchange rate is using the
> known dollar to peso exchange rate? I want to change pesos to dollars
> at the same rate I changed dollars to pesos.
In one direction of exchange you have:
(something)*(rate) = (something else)
You want the rate in the *other* direction such that exchanging back will
result in the original money you started with.
Remember, the pesos you now have (the "something else") are equivalent to
something*rate from the above equation. Well, what do you need to
multiply
(something)*(rate) by in order to get back the original "something?"
1/rate, right? That lets the r's essentially "cancel."
IOW, the two exchange rates are reciprocals of each other. In your case,
an
1100% (or simply "11") exchange rate in one direction means a 1/1100% (or
1/11) rate in the other direction. Since percent means parts of 100, this
results in:
1100% = 1100/100 = 11 ...for $ to pesos
1/1100% = 100/1100 = 1/11 ...for pesos to $
In your example, you exchange $1,000 for 1000*11 = 11,000 pesos, or
exchange
11,000 pesos for (11000)/11 = $1,000.
--
Darrell
--
submissions: post to k12.ed.math or e-mail to k12math@[EMAIL PROTECTED]
e-mail to the k12.ed.math moderator: kem-moderator@[EMAIL PROTECTED]
website: http://www.thinkspot.net/k12math/
newsgroup charter: http://www.thinkspot.net/k12math/charter.html
|
