If a man estimates his loss as 20% of the selling price, then his loss percent is = ?

According to the question,
Loss = 20% Selling price
$$i.e.\frac{{{\text{Loss}}}}{{{\text{Selling price}}}} = \frac{1}{5}$$
∴ Cost price = Selling price + Loss
= 5 + 1
= 6
$$\eqalign{ & \therefore {\text{Loss}}\% = \frac{1}{6} \times 100 \cr & \,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\, = \frac{{50}}{3}\% \cr} $$