A dishonest dealer use a scale of $90\, cm$ instead of a metre scale and claims to sell at cost price. His profit is in $\%$

The labelled price of a cupboard is $Rs$ $6500 .$ The shopkeeper sold it by giving $5 \%$ discount on the labelled price and earned a profit of $15 \% .$ What approximately is the cost price of the cupboard? (in $Rs.$)

A cab driver makes a profit of $20 \%$ on every trip when he carries $3$ passengers and the price of petrol is $Rs.\,30$ a litre. Find the percentage profit for the same journey if he goes with four passengers per trip and the price of petrol reduces to $Rs.\, 24$ a litre? (in $\%$)

(Assume that revenue per passenger is the same in both the cases.)

Abhishek purchased $140$ shirts and $250$ trousers at $Rs.\, 450$ and at $Rs.\, 550$ respectively. What should be the overall average selling price of shirts and trousers so that $40 \%$ profit is earned? (in $Rs.$)

(rounded off to next integer)

A tradesman gives $4 \%$ discount on the marked price and gives $1$ book free for buying every $15$ books and thus gains $35 \% .$ The marked price is increased above the cost price by (appx.) (in $\%$)

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