Inverse Percentage.

Question

Sorry for asking this foolish question.

Here is the data i have. I purchased the product as $5 and additional fee is 2%. So Here is the total dollor $total = 5 + (5*2/100) = 5.1 total dollor i have. But now i want to revert back to original price

in this case i have the data as only 
total amount

$5.1 and 2% fee.

How can i revert back to $5 based on the above data.

Thanks

Answer 1

It appears from your calculation that the additional fee is $2$ percent of the price, not $\$2$. That means that if the base price is $p$, the total cost $t$ is $t=p+0.02p=1.02p$. Thus, $p=\frac{t}{1.02}$.

In your example, for instance, this leads to the calculation

$$p=\frac{5.1}{1.02}=5\;,$$

as it should.

Answer 2

Let the original amount be $x$.

Then, $x+x\left(\frac{2}{100}\right)=5.1$

which gives $x=5$.