$A$ machine is sold at a profit of $15 \%$. Had it been sold for $Rs\, 540$ more,$24 \%$ would have been gained. Find the cost price.

$A$ shopkeeper sold an article offering a discount of $5 \%$ and earned a profit of $23.5 \% .$ What would have been the percentage of profit earned if no discount was offered?

$A$ man buys an article for $Rs. 27.50$ and sells it for $Rs. 28.60$. Find the gain percent. (in $\%$)

$A$ dealer fixed the price of an article $40 \%$ above the cost of production. While selling it,he allows a discount of $20 \%$ and makes a profit of $Rs. 48$. The cost of production (in $Rs.$) of the article is:

$A$ man bought some fruits at the rate of $16$ for $Rs. 24$ and sold them at the rate of $8$ for $Rs. 18$. What is the profit percent (in $\%$)?

Paras Health Care made $3000$ strips of vitamin tablets at a cost of $Rs. 4800$. The company gave away $1000$ strips of tablets to doctors as free samples. $A$ discount of $25\%$ is given on the printed price. Find the ratio of profit in $Rs.$ if the price is raised from $Rs. 3.25$ to $Rs. 4.25$ per strip and if at the latter price,samples to doctors were done away with.