$A$ trader buys $500 \, kg$ of cotton for $Rs. 9,000$. $10 \%$ of this cotton is spoiled due to rain. At what rate $(Rs./ kg)$ should he sell the rest to earn $10 \%$ profit?

Harkesh bought a certain quantity of tomato at the rate of $Rs. 1500$ per quintal. $10 \%$ of the tomato was spoiled. At what price in $Rs.$ per quintal should he sell the remaining to gain $20 \%$ of his outlay?

$A$ man sold two cows at $Rs. 1995$ each. On one he lost $10\%$ and on the other he gained $10\%$. What is his gain or loss percent (in $\%$)?

An article is marked for sale at $Rs. 504$. The shopkeeper gives a discount of $5\%$ on the marked price and still earns a profit of $20\%$. What is the cost price of the article? (in $Rs.$)

By selling cloth at $Rs. 9$ per meter,a shopkeeper loses $10 \%$. Find the rate at which it should be sold so as to earn a profit of $15 \%$ (in $Rs.$).

$A$ merchant purchases a wrist watch for $₹ 450$ and fixes its list price in such a way that after allowing a discount of $10 \%$,he earns a profit of $20 \%$. Then the list price (in rupees) of the wrist watch is