In order to find the rate of the discount the percentage must be equal to the difference of the regular price and the discounted price.
[tex]Rate= \frac{Percentage}{Base} = \frac{499.95-299.95}{499.95} = \frac{200}{499.95} = \frac{20000}{49995} =0.40004[/tex]
Therefore the rate is approximately 0.40004*100%=40.00%