The marked price is above the cost price by
Let cost price be
Let Marked Price be
The tradesman gives 4% discount on the marked price,
That means selling price
He gives 1 article free for buying every 15 articles
That means when he sells 16 items for Selling Price of 15 items.
Cost price for 16 items will be :
He gains 35% ,
equating (4) and (5):
So, the marked price is 50% more than the cost price.
The marked price is above the cost price by=
That means, the trader buys each item for $100, marks them $150 each and sells them at $144 (after 4% discount).
He sells 16 items for selling price of 15. So instead of charging $2304 for 16 items, he charges $2160 for 16 items, and gains ($ 560) i.e. 35 % of the cost price.