Amit purchased $13$ chairs for $Rs. 115$ each and sold all of them for $Rs. 1220$. Find the profit or loss on the transaction.

$A$ person incurs a $5 \%$ loss by selling a watch for $Rs. 1140$. At what price should the watch be sold to earn a $5 \%$ profit?

$A$ $TV$ set is being sold for $Rs. x$ in Chandigarh. $A$ dealer went to Delhi and bought the $TV$ at a $20\%$ discount (from the price of Chandigarh). He spent $Rs. 600$ on transport. Thus,he sold the set in Chandigarh for $Rs. x$,making a $14 \frac{2}{7}\%$ profit. What was $x$ in $Rs.?$

Anil bought an item with $12 \frac{1}{2} \%$ discount on the labelled price. He sold the item with $17 \frac{1}{2} \%$ profit on the labelled price. What was his percent profit on the price he bought?

Mahesh purchased $25\, kg$ of rice at $Rs. 32$ per $kg$ and $15\, kg$ of rice at $Rs. 36$ per $kg.$ He mixed the two varieties of rice and sold it at $Rs. 40.20$ per $kg.$ What is the percent profit earned (in $\%$)?

Ravi purchases $90$ pens and sells $40$ pens at a gain of $10 \%$ and $50$ pens at a gain of $20 \%$. Had he sold all of them at a uniform profit of $15 \%$,he would have got $Rs. 40$ less. Find the cost price of each pen in $Rs$.