If the $CP$ of $50$ items is equal to the $SP$ of $40$ items,then what is the profit or loss $\%$ (in $\%$)?

$A$ man bought $15$ mangoes for a rupee. How many mangoes were sold for a rupee so that there is a loss of $25 \% ?$

The marked price of an article is $Rs. 5000$. Due to a special festive offer,a certain percentage of discount is declared. Mr. $X$ availed this opportunity and bought the article at the reduced price. He then sold it at $Rs. 5000$ and thereby made a profit of $11 \frac{1}{9} \%$. The percentage of discount allowed was:

$A$ man sold two watches for $Rs. 3750$ each. On one he gained $5 \%$,and on the other,he lost $5 \%$. What was his total gain or loss percentage?

$A$ man gains $15 \%$ by selling a calculator for a certain price. If he sells it at triple the price,then what will be the profit percentage (in $\%$)?

Two items $A$ and $B$ are sold at a profit of $10 \%$ and $15 \%,$ respectively. If the amount of profit received is the same,then the cost price of $A$ and $B$ may be (in $Rs.$)