If on selling $12$ note books, a seller makes a profit equal to selling price of $4$ notebooks. What is his percent profit?

By selling an article for $Rs$ $384,$ a trader gains $20 \%$. Find the cost price of article.

The value of an article depreciates every year at the rate of $10 \%$ of its value. If the present value of the article is $Rs.\, 729$, then its worth $3\, years$ ago was (in $Rs.$)

A trader purchase a wrist watch and a pendulum for $Rs.$ $390.$ He sells them making a profit of $10 \%$ on the watch and $15 \%$ on the pendulum. He earns a profit of $Rs$. $51.50 .$ The difference between the original prices of the pendulum and the watch is equal to? (in $Rs.$)

A shopkeeper listed the price of goods at $30 \%$ above the cost price. He sells half the stock at this price, one fourth of the stock at a discount of $15 \%$ and the remaining at $30 \%$ discount. His overall profit is.......$\%$

Arun marks up the computer he is selling by $20 \%$ profit and sells them at a discount of $15 \%$. Arun's net gain percent is