The percentage profit earned by selling an article for $Rs. 1920$ is equal to the percentage loss incurred by selling the same article for $Rs. 1280$. At what price should the article be sold to make $25 \%$ profit? (in $Rs.$)

$A$ shopkeeper bought $30\, Kg$ of wheat at the rate of $Rs.\, 45$ per $Kg$. He sold $40\%$ of the total quantity at the rate of $Rs.\, 50$ per $Kg$. Approximately,at what price per $Kg$ should he sell the remaining quantity to make $25\%$ overall profit? (in $Rs.$)

$A$ trader purchases a wrist watch and a pendulum for $Rs. 390$. He sells them making a profit of $10 \%$ on the watch and $15 \%$ on the pendulum. He earns a total profit of $Rs. 51.50$. The difference between the original prices of the pendulum and the watch is equal to? (in $Rs.$)

The cost price of $100$ books is equal to the selling price of $60$ books. The gain percentage or loss percentage is:

An electric pump was sold at a profit of $15 \%$. Had it been sold for $Rs. 600$, the profit would have been $20 \%$. What was the former selling price in $Rs.$?

If the selling price of an article is $\frac{4}{3}$ of its cost price,the profit percentage in the transaction is: (in $\%$)