A seller offers discounts on the basis of the numbers of articles are bought. He gives a discount of 20% when 15 articles are bought and a discount of 15% when 20 articles are bought. If the loss, he bears in each case is the same, find the ratio of marked price and cost price.

1 : 1

Loss = CP - SP            SP = MP × \(\frac{100 -x}{100}\) - discount

Discount 20% = \(\frac{1}{5}\) = \(\frac{4}{5}\)

and 15% = \(\frac{3}{20}\) = \(\frac{17}{20}\)

ATQ,

15 [ CP - MP × \(\frac{4}{5}\)] = 20 [ CP - MP × \(\frac{17}{20}\)]

                    MP = CP

Now → MP     :     CP

             1     :     1