Find $SP$ when $CP = Rs. 56.25$ and $\text{Gain} = 20\%$?

If the ratio of the cost price and selling price of an article is $20: 21$,then what will be the profit percent (in $\%$)?

$A$ sells an article to $B$ at a profit of $20 \%$ and $B$ sells it to $C$ at a loss of $10 \%$. If $C$ pays $Rs. 540$ for it,at what price did $A$ buy?

$A$ man sells an article at a loss of $5 \%$. If he had bought it at $20 \%$ more and sold it for $Rs. 115$ less,he would have made a loss of $40 \%$. Find the cost price of the article.

On selling $17$ balls at $Rs. 720$,there is a loss equal to the cost price of $5$ balls. The cost price of a ball is (in $Rs.$)

By selling an article for $Rs. 21$,a man incurs a loss such that the percentage loss is equal to the cost price. The cost price of the article is (in $Rs.$):