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

A dealer buys an article listed at $Rs.\, 100$ and gets successive discounts of $10 \%$ and $20 \% .$ He spends $10 \%$ of the Cost Price on transportation. At what price should he sell the article to earn a profit of $15 \% ?$ (in $Rs.$)

A dairyman pays $Rs.\, 6.40$ per litre of milk. He adds water and sells the mixture at $Rs.\, 8$ per litre, thereby making $37.5\%$ profit. The proportion of water to milk received by the customers is

A person sells $36$ apple per rupee and suffers a loss of $4 \% .$ Find how many apple per rupees to be sold to have a gain of $8 \%$.

A white goods dealer pays $10 \%$ custom duty on an i-phone that costs $Rs.\, 25000$ in $UK$. For how much should hemark it, if he desires to make a profit of $20 \%$ after giving a discount of $25 \%$ to the buyer? (in $Rs$)

A shopkeeper professes to sell his goods at cost price but uses a weight of $800\, g$ instead of kilogram weight. Thus, he makes a profit of