$A$ sells an article to $B$ at a gain of $25 \%$,$B$ sells it to $C$ at a gain of $20 \%$,and $C$ sells it to $D$ at a gain of $10 \%$. If $D$ pays $₹ 330$ for it,how much did it cost $A$? (in $₹$)

$A$ manufacturer undertakes to supply $2000$ pieces of a particular component at $Rs. 25$ per piece. According to his estimates,even if $5\%$ fail to pass the quality tests,he will make a profit of $25\%$. However,as it turned out,$50\%$ of the components were rejected. What is the loss to the manufacturer? (in $Rs.$)

$A$ 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 $CP$?

$A$ shopkeeper purchases two items for $Rs. 520$. One of them is sold at a gain of $16\%$ and the other at a loss of $10\%$,thus making no profit or loss. What is the selling price of the item sold at a loss?

$A$ man bought $500$ metres of electronic wire at $50$ paise per metre. He sold $50 \%$ of it at a profit of $5 \%$. At what percent should he sell the remainder so as to gain $10 \%$ on the whole transaction?

If Aditya sells an article to Nutan at $10 \%$ gain,while Nutan sells it to Manish at $20 \%$ gain at $Rs. 1914$,then what is the Cost Price in $Rs.$?