cost price of $100$ books is equal to the selling price of $60$ books. The gain percentage or less percentage is

An article is marked for sale at $Rs.$ $504 .$ The shopkeeper gives a discount of $5 \%$ on the sale price and still earns a profit of $20 \% .$ What could be the purchase price of the article? (in $Rs.$)

A discountof $40 \%$ on the marked price of atrouser enables Ajit to purchase a shirt also which costs him $Rs.\,320.$ How much did Ajit payfor the trouser? (in $Rs.$)

Raheem sells a machine for $RS.\,48$ lakh at a loss. Had he sold it for $RS.\, 60$ lakh, his gain would have been 5 times the former loss. Find the cost price of the machine. $Rs.$ in lakh ?

$'A ^{\prime}$ sells an article to $'B ^{\prime}$ at a gain of $20 \%$ and $' B ^{\prime}$ sells it to $'C ^{\prime}$ at a gain of $10 \%$ and $'C ^{\prime}$ sells it to $'D'$ at a gain of $12 \frac{1}{2} \%$. If ${ }^{\prime} D$ ' pays $Rs.\, 29.70$ what did it cost to $'A ^{\prime} ?$ (in $Rs.$)

The cost price of an article is $64 \%$ of the marked price. The gain percentage after allowing a discount of $12 \%$ on the marked price is........$\%$