Find $SP$ when $CP = Rs. 80.40$ and $\text{loss} = 5\%$.

Ram sells an article to Girish at a gain of $20 \%$,Girish sells it to Sanjay at a gain of $10 \%$,and Sanjay sells it to Aditya at a gain of $12 \frac{1}{2} \%$. If Aditya pays $Rs. 59.40$,what did it cost Ram in $Rs.$?

Nutan pays $Rs. 2140$ for $3$ calculators and $4$ pens,while she pays $Rs. 1355$ for $1$ additional calculator and $5$ pens. What is the cost of a calculator in $Rs.$?

By selling an article for $Rs. 384$,a trader gains $20 \%$. Find the cost price of the article.

An article is sold at a certain fixed price. By selling it at $\frac{2}{3}$ of that price,one loses $10 \%$. The gain percent on selling it at the original price is

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