A man gains $15 \%$ by selling a calculator for a certain price. If he sells it at the triple the price, then what will be the profit percentage?

A shopkeeper mixes $26\, kg$ of wheat which cost $Rs$. $20$ a $kg$ with $30\, kg$ of wheat which cost $Rs.\,36$ a $kg$ and sells the mixture at $Rs.\,30$ a $kg.$ Find the profit percent.

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)

Albert buys $4$ $horses$ and $9$ cows for $Rs. 13400$. If he sells the horse at $10 \%$ profit and the cows at $20 \%$ profit, then he earns a total profit of $Rs.\, 1880 .$ The cost of a horse is (in $Rs.$)

$'A ^{\prime}$ sells a good to $'B ^{\prime}$ at a profit of $10 \%$ and $B$ sells it to $'C ^{\prime}$ at a profit of $20 \% .$ Find out the resultant profit. (in $Rs.$)

On selling $17$ balls at $Rs.\, 720$, there is a loss equal to the cost price of 5 balls. The cost price of a ball is (in $Rs.$)