Re: Math Formula Question - Need Ideas [message #184515 is a reply to message #184514] |
Sun, 05 January 2014 00:33 |
Richard Damon
Messages: 58 Registered: August 2011
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On 1/4/14, 7:26 PM, Adrienne Boswell wrote:
> I have a math question to which I can't find the answer. Here is the
> scenario:
>
> Someone goes to a store and has $100.00 worth of items. The merchant
> gives the customer a 10% discount, so only $90.00 is sent to the bank.
> Of the original amount, $10.00 goes to the customer for the discount,
> $80.00 goes to the merchant, $10.00 goes for a processing fee. But those
> amounts have to be calced on the original amount, not what the bank got.
> I need a formula to find the original amount if I have the percentage
> (10%) and the amount the bank got ($90.00). I know in my head that the
> original amount is $100.00, but I have to do it programatically.
>
> I know this is probably dead simple, but I just can't get my head around
> it.
>
> Thanks in advance.
>
10% is 0.1
You got the $90 by multiplying the original $100 by (1-0.1) to get $90,
so you can divide the $90 by (1 - 0.1) to get the original $100
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