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 $Rs.$?

$A$ fruit seller bought $240$ bananas at the rate of $Rs. 48$ per dozen. He sells half of them at the rate of $Rs. 5$ per banana. $\frac{1}{6}$ of the remaining bananas are found to be rotten. At what price per banana must he sell the remaining bananas to get a profit of $25\%$ on his entire investment?

Find $CP$ when $SP = Rs. 51.70$ and $\text{loss} = 12\%$.

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 buys $10$ oranges for a rupee and sells $8$ oranges for a rupee. What is the profit percent?

$A$ retailer offers the following discount schemes for buyers on an article:
$I.$ Two successive discounts of $10 \%$
$II.$ $A$ discount of $12 \%$ followed by a discount of $8 \%$
$III.$ Successive discounts of $15 \%$ and $5 \%$
$IV.$ $A$ discount of $20 \%$
The selling price will be minimum under the scheme: