A dealer offers a cash discount of 20% and still makes a profit of 20%, when he further allows 16 articles to a dozen to a particularly sticky bargainer. How much percent above the cost price were his wares listed?

Explanation:-

Let the CP of the article be Rs. x, since he earns a profit of 20%, hence SP= X + 20% of X = 1.2x.
It is given that he incurs loss by selling 16 articles at the cost of 12 articles [loss = ^(16-12)/₁₆ = 25%]
His selling price = SP - 25% of SP = SP*0.75;
Hence, SP*0.75 = 1.2X.
Or, SP = (1.2*^x/_0.75) = 1.6X.
This SP is arrived after giving a discount of 20% on MP.
Let MP = Y.
Y - 20% of Y = SP
0.80Y = 1.6X.
Y = 2X.
It means that the article has been marked 100% above the cost price. Or Marked Price was twice of cost price.