The formula for calculating the Trade Receivables Turnover Ratio is:

Net Credit Revenue from Operations/Average Trade Receivables

The correct answer is option 3- Net Credit Revenue from Operations/Average Trade Receivables.

Trade Receivable Turnover ratio = Net Credit Revenue from Operations/Average Trade Receivable
[Where Average Trade Receivable = (Opening Debtors and Bills Receivable + Closing Debtors and Bills Receivable)/2]
It needs to be noted that debtors should be taken before making any provision for doubtful debts.