20% loss on selling price is what percent loss on the cost price?

20% loss on selling price.

= \(\frac{20}{100}\)

Let us assume that  Selling price = 100 , Loss = 20

and Cost price = 100 + 20 = 120

Now,

Loss percentage on Cost price

= \(\frac{20}{120}\) 

= \(\frac{1}{6}\)

= 16.66%