If the selling price of $50$ articles is equal to the cost price of $40$ articles,then the loss or gain percent is:

$A$ person sells two articles,each for $Rs. 1040$. He incurs a $20\%$ loss on the first and a $10\%$ loss on the second. Find the overall percentage loss. (in $\%$)

$A$ fruit seller sells mangoes at the rate of $Rs. 9$ per $kg$ and thereby loses $20\%$. At what price per $kg$ should he have sold them to make a profit of $5\%$? (in $Rs.$)

If a shopkeeper sells $25$ articles at $Rs. 45$ per article after giving $10 \%$ discount and earns $50 \%$ profit. If the discount is not given,what is the profit percentage gained?

The printed price of an article is $40 \%$ higher than its cost price. What is the discount rate so that the seller gains a $12 \%$ profit?

If the $CP$ of $13$ bats is $Rs. 390$,what is the selling price in $Rs.$ when it is sold at a $10 \%$ loss?