how to calculate VAT percentage from VAT rupees in C#?

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C#

WinForms

mathematics

I created a function that will return the VAT percentage from Total and VAT amount..
My Function is :-

public decimal vatRsToPer(decimal vatAmt, decimal totalAmt)
        {
            try
            {
                decimal rupees;
                rupees = decimal.Multiply(vatAmt, 100m);
                rupees = decimal.Divide(rupees, totalAmt);
                return rupees;
            }
            catch {
                return 0m;
            }
        }

Problem is, suppose the total amt is "2400.00" and VAT% is "4", that means the VAT Rupees is "96.00"..
If i want to get the percentage of the VAT from that VAT rupees "96.00" and Total rupees "2496.00"(which is including VAT rupees). then my function return "3.85" not "4"..
Please Help me, Where I did wrong....

Every Suggestion will be appreciated...