$A$ man sold a cow at a loss of $12 \%$. If he had sold it at a gain of $6 \%$,he would have received $₹ 72$ more. What was the cost price of the cow?

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 $Rs$.

Ramesh purchased a bicycle for $Rs. 5200$ and spent $Rs. 800$ on its repairs. He had to sell it for $Rs. 5500$. Find out his profit or loss percent.

$A$ shopkeeper sells notebooks at the rate of $Rs. 457$ each and earns a commission of $4\%$. He also sells pencil boxes at the rate of $Rs. 80$ each and earns a commission of $20\%$. How much total commission will he earn in two weeks if he sells $10$ notebooks and $6$ pencil boxes a day?

$A$ shopkeeper sells $20$ pencils for the same amount of money as he paid for $25$ pencils. What is his gain percent?

$A$ dealer sold two types of goods for $Rs. 10,000$ each. On one of them,he lost $20 \%$ and on the other he gained $20 \%$. His gain or loss per cent in the entire transaction was