By selling $80$ ball pens for $₹ 140$,a retailer loses $30 \%$. How many ball pens should he sell for $₹ 104$ so as to make a profit of $30 \% ?$

$A$ shopkeeper purchased $150$ identical pieces of furniture at the rate of $Rs. 250$ each. He spent an amount of $Rs. 2500$ on packing. He fixed the price of each furniture at $Rs. 320$. However,he decided to give a discount of $5 \%$ on the labeled price. What is the percent profit earned by him (in $\%$)?

$A$ shopkeeper professes to sell his goods at cost price but uses a $930 \text{ g}$ weight instead of $1 \text{ kg}$ weight. What will be the profit percentage of the shopkeeper (in $\%$)?

If the cost price of $20$ articles is equal to the selling price of $15$ articles,find the profit percent?

Kritika bought $25$ $i-pads$ and $i-phones$ for $Rs. 205000$. She sold $80\%$ of the $i-pads$ and $12$ $i-phones$ for a profit of $Rs. 40000$. Each $i-pad$ was marked up by $20\%$ over cost and each $i-phone$ was sold at a profit of $Rs. 2000$. The remaining $i-pads$ and $3$ $i-phones$ could not be sold. What is Kritika's overall profit/loss?

Some articles were bought at $6$ articles for $Rs. 5$ and sold at $5$ articles for $Rs. 6$. The gain percent is: (in $\%$)