The cost price of $20$ articles is the same as the selling price of $x$ articles. If the profit is $25 \%$,then the value of $x$ is:

$A$ shopkeeper sells an article at a gain of $10 \%$. Had he sold it at a loss of $20 \%$,its selling price would have been $Rs. 180$ less. What is the cost price of the article? (in $Rs.$)

If $11$ mangoes are bought for $Rs. 10$ and sold at $10$ for $Rs. 11$,what is the gain or loss percentage (in $\%$)?

$A$ 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.

$A$ and $B$ jointly made a profit of $Rs. 1650$ and they decided to share it such that $\frac{1}{3}$ of $A$'s profit is equal to $\frac{2}{5}$ of $B$'s profit. Then the profit of $B$ is (in $Rs.$)

$A$ shopkeeper earns a profit of $12 \%$ on selling a book at $10 \%$ discount on the printed price. The ratio of the cost price and the printed price of the book is