On an order of $5$ dozen boxes of a consumer product, a retailer receives an extra dozen free. This is equivalent to allowing him a discount of:
- $15\%$
- $\frac{97}{6}\%$
- $\frac{50}{3}\%$
- $20\%$
So, for every 5 dozen he orders, he gets 1 dozen free. This is equivalent of paying for only $\frac{5}{6}$ of your order, therefore, $\frac{1}{6}$ discount.
To convert this to percentage we multiply by 100 to get $\frac{1}{6} \times 100 = \frac{50}{3}$.
So the answer is 3.