Three successive discounts of $10 \%$,$12 \%$,and $15 \%$ are equivalent to a single discount of what percentage (in $\%$)?

Hemant purchased $120$ rims of paper at $Rs. 80$ per rim. He spent $Rs. 280$ on transportation,paid octroi at the rate of $40$ paise per rim,and paid $Rs. 72$ to the coolie. If he wants to have a gain of $8 \%$,the selling price per rim must be (in $Rs.$)

On a certain item,the profit is $150 \%$. If the cost price increases by $25 \%$,what will be the new profit margin (in $\%$)?

Ajit calculates his profit percentage on the selling price,whereas Rohit calculates his on the cost price. They find that the difference between their profits is $Rs. 100$. If the selling price for both of them is the same and both of them get a $25\%$ profit,find their selling price (in $Rs.$).

$A$ 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 (approx.) (in $\%$).

At a cost of $60$ paise per article,Sarika produces $750$ articles. She sets the selling price such that if only $600$ articles are sold,she would have made a profit of $40 \%$ on the total outlay. However,$120$ articles got spoilt and she was able to sell $630$ articles at this price. Find her actual profit or loss percent as a percentage of the total outlay,assuming that the unsold articles are useless.