If $11$ mangoes are bought for $Rs. 10$ and sold at $10$ for $Rs. 11$,what is the gain or loss percentage (in $\%$)?

Sanjay purchased a chair marked at $Rs. 800$ at $2$ successive discounts of $10 \%$ and $15 \%$ respectively. He spent $Rs. 28$ on transportation and sold the chair for $Rs. 800$. How much is his gain percentage (in $\%$)?

$A$ bakery bakes cakes with the expectation that it will earn a profit of $40 \%$ by selling each cake at the marked price. During delivery to the showroom, $16 \%$ of the cakes were completely damaged and could not be sold. $24 \%$ of the cakes were slightly damaged and were sold at $80 \%$ of the cost price. The remaining $60 \%$ of the cakes were sold at the marked price. What is the percentage profit on the whole consignment (in $\%$)?

$A$ tradesman gives $4 \%$ discount on the marked price and gives one article free for buying every $15$ articles and thus gains $35 \%$. The marked price is approximately how much percent above the $CP$?

$A$ man bought apples at the rate of $8$ for $Rs. 34$ and sold them at the rate of $12$ for $Rs. 57$. How many apples should be sold to earn a net profit of $Rs. 45$?

$A$ dealer buys a table listed at $Rs. 600$ and gets successive discounts of $10\%$ and $20\%$. What is his profit or loss percent if he sells it at $Rs. 540$?